Furnishing with Fungi

This BBC podcast is supported by ads outside the UK.

Want to stop engine problems before they start?

Pick up a can of C Foam Motor Treatment.

C-Foam helps engines start easier, run smoother, and last longer.

Trusted by millions every day, C-Foam is safe and easy to use in any engine.

Just pour it in your fuel tank.

Make the proven choice with C Foam.

Available everywhere.

Automotive products are sold.

Seafoam!

BBC Sounds, music, radio, podcasts.

I'm Hannah Fry.

And I'm Dara O'Brien.

And this is Curious Cases.

The show where we take your quirkiest questions, your crunchiest conundrums, and then we solve them.

With the power of science.

I mean, do we always solve them?

I mean, the hit rate's pretty low.

But it is with science.

It is with science.

Hannah.

Yes.

How are you on like a nice mushroom risotto?

I'd say medium.

How do you feel about a nice yeasty beer?

I mean, you didn't make it sound that nice when you said yeasty.

Yeah, I think I leaned into yeasty, but that is kind of where we're getting at here.

Less keen.

Okay, then for the last of the Trinity, a nice batch of athlete's foot.

I would say you really are sliding down the scale.

I thought mushroom risotto was the bad end, but no.

No, that was supposed to be the lure.

And then, no.

The point is, they're all made of fungi.

Okay.

Yeah.

Great.

Thank you.

Are we doing an entire episode on yeast infection?

No, no, we are not.

It's about things that are made of fungi.

Of all of the different ways that you could have introduced this programme, I'm so pleased that that was one you were asking.

And it easily will be the last mention of risotto.

It used to be Orati's foot.

Are we just showing the broad range of the shape, you know, how variable fungus are?

I tell you what, I want to do it.

I want to hear the clip from the listener.

I want to hear your raw material.

So I know what you use to connect with that in the middle.

Okay, what I'm trying to introduce came from a listener called Alexis.

Hi, I'm Alexis.

I'm from Arrington.

So I'd like to know how much of what we have in the home could be grown using fungi or materials from fungi.

So, I don't use fungi products

apart from eating them, but I'm so intrigued to see how things are going to advance and the technologies are going to advance with fungi.

Athlete's foot.

Yeah.

Okay, look, obviously, we have to eliminate quickly the thought that Alexis is, in fact, a gnome.

Sure.

I like the idea that she's just, you know, calling us in from her toad store.

Oh, I'm so sweet.

With a little fishing rod.

Yeah.

And then she listens to the show, she's fishing for whatever they fish for.

Red and white one.

Red and white one like.

But would you like to think that where you're living is made of mushrooms?

I mean, as long as you don't have to eat them or.

No, you don't have to eat your way in and eat your way out.

It just feels a bit gross, doesn't it?

I don't know why.

And yet, a lovely mushroom.

Look at the pizza.

Very nice.

Very nice.

This isn't about the aesthetics of mushrooms, though, is it?

This is about the functional uses.

Absolutely.

So utility.

And the fact that we may be able to create really, really interesting materials with them.

Would you live in a mushroom house?

Well, I mean, if it's like literally a giant mushroom with a door in it, and you go in and you hear dip, dip, dip, dip, dip, dip, dive, the footsteps, and then they appear at the top on the crown.

Yeah, that'd be amazing.

That'd be lovely.

But I'd be the only one

on my road.

I mean, it'd be tough to get the planning permission for that.

It certainly would.

Well, joining us to build mushroom houses today, we have Phil Ayres, who is the Professor of Biohybrid Architecture at the Royal Danish Academy.

And Katie Field, Professor of Plant Soil Processes at the University of Sheffield.

Katie, we need some fungal 101, essentially.

And I would say that a lot of this is because of its, you know, fungi have a kind of a bad press, you know, it's damp, it's dark, what's that growing in?

Yeah, completely unwarranted, of course.

So the kingdom of fungi, and it is its own kingdom, right?

So a lot of people just think that it's part of plants, and historically, fungi have been classified as plants.

But yeah, they're their own kingdom, and they're suitably diverse.

In terms of numbers of species, we know about and have described just over 100,000.

But actually the best estimates suggest there's probably about 6 million plus.

Right, so we only know about a very small fraction of species of fungi.

Is one of those species a red and white toadstool?

Yes.

Does it actually exist for real?

Oh my goodness, yes.

An Amanita.

Yes, Amanita muscoides.

Yeah, fabulous.

Fly agaric.

Where do they grow them?

In woodlands, all all over the place.

You just need to walk through the woods.

In the UK.

Yeah.

Yeah, loads.

There's loads of them in the peat district.

Interesting.

You need to get out of here.

Yeah, yeah, absolutely.

They're fascinating.

Obviously, don't eat them.

They're a bit toxic.

But actually, foxes nibble them and they kind of get a bit of a hallucinogenic rush from them.

Yeah, yeah.

So you can find all these spaced out corporations.

What you want from foxes is even worse behaviour.

And that's

a lot of fun.

Psychedelic foxes.

Yeah, yeah.

One other fungus 101.

Do they grow out of corpses?

corpses?

I guess if you leave a corpse out long enough,

you know, the fungal kingdom encompasses some really important environmentally relevant groups, and part of that is the decomposers.

And without these decomposing fungi, we would be, I mean, we'd be buried in detritus, so dead bodies, leaf litter.

dead plants, everything.

So this is basically the machinery that tidies all that up.

Yeah, yeah.

Well, they're the primary decomposers.

So you do get a bit of bacterial stuff, but fungi are the main powerhouses of decomposition in the natural environment so they're they're they they're unlike i always think of fungi more as like alien life forms they're not you cannot relate to a fungus okay so it doesn't eat in the same way that we eat so it doesn't eat something at one end and then pass it out the other end okay they grow through their food right so that as it would almost be like for me i would like to live in ice cream and just eat my way through a swimming pool of ice cream and that would be my life.

But you would become the swimming pool of ice cream.

Yeah, no,

only.

So, a fungus will grow through its food, and it'll digest it from the tips of the hypha.

So, that's the long filaments that make up the main vegetative body of the fungus.

And it'll digest stuff.

It secretes enzymes that decompose organic material, and then it'll assimilate all of those nutrients that are coming out of what it's digested.

And then it'll just build more fungus, it'll build more hyphal mycelium, and it'll grow and branch and form this massively complex network.

And as hypha sort of turn over, so they die and retract, you're left with fungal skeletons almost like the really strong cell walls that make up fungal filaments, are left behind.

And that kind of, in a way, it locks carbon up within soils or decaying stuff in a way, because it's very hard to degrade that tough skeleton of the fungus, if you like.

The question was about mushrooms, right?

And now we're talking about funguses or fungi.

Where, like, what's the relation between one and the other?

Are like all mushrooms fungi and not all fungi mushrooms?

So, all mushrooms are fungi.

Okay, so the main body of a fungus is the mycelium, and that is the thread-like filamentous network that forms the main body of it.

That's what does the eating, that's what does the growing and colonizing new areas.

And when the conditions are right,

the fungus will, or some groups of fungi, will produce a mushroom, and the mushroom is the reproductive fruiting body, if you like, of the fungus.

The whole thing, both the stalk and the head.

Absolutely.

Yeah, I mean, there's a huge diversity again in formation and structure of mushrooms.

Some of them have stalks, like your classic toadstool mushroom, others don't, and they grow like brackets on a tree.

You've probably seen bracket fungi.

There's also ones that look like bits of coal.

There's a huge diversity of mushrooms, but they're all the fruiting bodies.

But what I think is really mind-blowing is that when you see a mushroom, you think like, oh, I've seen a fungus, you know, that is just the tip of the iceberg for that organism.

There's probably hundreds of meters of hyphae associated with that mushroom that's actually the main part of the fungus.

So, hang on, so if you're farming for mushrooms, is there kind of a huge plant from which you are drawing the mushrooms that we would get in a little punish and then we'd stick into a pasta?

They're all the fruit that are taken off a larger.

Absolutely, absolutely.

So, the sort of mushroom farms where you get your supermarket mushrooms.

I'm thinking the little button mushrooms, yeah.

So, the fungus that's responsible for producing those is a decomposer, so it doesn't need a living plant to live.

So, essentially, it'll be growing in a tray of what is unrotted compost.

It's just sort of

plant detritus.

And then, when you'll be growing it in conditions that will suit the growth of the mycelium, but then it'll produce fruit.

You want it to spall.

I you remember early on how I said there was something a bit gross about mushrooms?

I'd like to double down on this comment.

Oh,

do they bad people?

Do they live in mushrooms?

No, I think people associate fungi with sort of decay and disease, right?

And that isn't fair.

That is just one of their functions.

You know, we need to be more thinking about them as sort of engineers of the world around us, right?

I mean, we could even go as far as to say that without fungi, we wouldn't be here today.

There would be no plants, there would be no atmosphere that we could breathe.

So really we owe a lot to fungi.

I mean team fungus over here.

Goodness me.

Okay well somebody else who's on team fungus, Phil, I know that you're an architect, right?

I know that you're you're trying to do some quite surprising things with fungi that don't involve making risottos.

Can you tell us a little bit about your project?

Yeah so we're looking at trying to create new kinds of materials using fungi as a binder.

So we have particles of dead matter, typically wood, and the fungus will grow through that and bind it.

And from there we can create functional material units.

Let me understand this though.

Okay, so you say you take dead wood.

Are we talking like sawdust here?

Exactly.

So get some sawdust and then what do you actually do with it?

So if you've ever made bread, the recipe is similar.

So what you're doing is you're taking your sawdust, you're adding a quantity of water, and then you introduce the fungus into that.

Like a bit of yeast.

Exactly.

And then you allow it to ferment for a period.

And then once it's reached the properties that you want, you stick it in the oven and you bake it.

No!

So you're baking only at about 60 degrees.

That's enough to do what we call denaturing.

And then, okay, but then, oh, oh, denaturing because you're trying to kill the fungus from growing more.

Exactly, yeah.

And then what does the final product look like?

Like, would you be able to, does it have the same properties as like like a traditional brick?

Well,

more towards the foam or medium density fibre board.

But the research that's going on is really trying to improve the properties that can be achieved.

So sorry, medium density fibre board, right?

Are we talking like garden shed?

You could make a garden shed, but not a house.

At the moment, we're

really looking at interior materials.

So the idea of actually growing a house,

which is actually the EU-funded project we had about five years ago, the ambition there was to look at the idea that we could grow a house monolithically.

What do you mean by monolithically?

Like as in one...

So in one hit.

So instead of growing multiple components and then building them together, could you set up a frame and then literally grow the house?

And that turns out to be really challenging because if you want particular kinds of material property, you need to give the fungus particular kinds of condition.

And at the scale of a building, you start to have differences in temperature, you've got gradients of gases, and these things begin to affect the properties of the material you're trying to grow.

So, currently, it's much more feasible to think about making components rather than monolithic houses.

Okay, we're still at the stage of gnome houses, then.

Gnome houses, possible.

Yes, yeah, yeah, yeah.

Human houses, not.

I quite quite like the idea of you just go, well, we're just going to plant this here, bang, boom, and then we'll come back and say that.

The nice thing, Dara, is you wouldn't have to wait six months.

So, this is one of the things that's really interesting about these materials compared to many bio-based materials that we use in architecture.

So, trees typically take 30 to 50 years to grow.

Bamboo is also something that we use quite regularly in architecture.

That can grow in a season, but it normally takes about three years for the tissues to reach a dense enough maturity.

But with mycelium, you can grow products in the space of two to three weeks.

And you can do that continuously,

making use of really available waste streams.

In this case, it becomes a really nice way of entering into a circular economy where we can be activating

agricultural, forestry, or even other kinds of industrial waste streams as the basis for growing the materials.

I mean, that really does undermine the recurring plot plot theme in Grand Designs of things running over project, doesn't it?

Yeah, yes.

If he comes back six months and go, no, we moved in five months ago.

The whole thing was done.

It was grand.

When never thought this would happen actually happens, Serve Pro's got you.

If disaster threatens to put production weeks behind schedule, Serve Pro's got you.

When you need precise containment to stay in operation through the unexpected, ServePro's got you.

When the aftermath of floods, wildfires, hurricanes, and other forces that are out of your control have you feeling a loss of control, ServePro's got you.

Simply put, whenever or wherever you need help in a hurry, make sure your first call is to the number one name in cleanup and restoration.

Because only ServePro has the scale and expertise to get you back up to speed quicker than you ever thought possible.

So, if fire or water damage ever threatens your home or business, remember to call on the team that's faster to any size disaster at 1-800SERVPRO or by visiting SurvePro.com.

ServePro, like it never even happened.

All right, so Phil's trying to build things, but our listener Alexis was also interested in things she could use in the home and their fact commercial companies using techniques as described by Phil to make products.

Here's the co-founder of an Italian company called Mogu.

Hello, everybody.

My name is Morizzi Simontalti.

I'm co-founder and chief mycelium officer of Skim, known as Mogu.

Our goal is essentially to disrupt the way things are traditionally made through active partnerships with fungi and with their mycelium.

What we do is to deliver bio-composite products that are primarily dedicated to interior design and interior architecture, and they comprise panels for acoustic absorption, wall panels for decorative purposes, as well as fluorine solutions.

There's different parameters we can affect when growing our mycelium biocomposite, starting from the hydration level of our feedstock, the temperature, and the pH of the substrate itself that makes it suitable and interesting for the fungus to digest it.

So, we are able, in fact, to guide the growth of the mycelium to create materials of a very even density, color, and overall quality in raw form that we easily can harvest at the end of the incubation process that takes just several weeks.

Can I just again just define mycelium?

Yeah, so mycelium is the main body of the fungus.

Right, okay.

It's the bit that grows, it's the bit that eats stuff.

It's basically this network of thread-like filaments that branch and connect and mesh together to form this web.

So what we think of as mushrooms, they're just a fruit.

That's just the apple on the tree.

Yes, yeah.

Okay, fine.

So, the bit that we've taught all this time is the useful bit is actually not the useful bit.

Well, it's pretty useful.

Mushrooms are delicious and very nutritious.

Okay, Grant, fine.

I'm sorry.

I'm never gonna hear a bad word about fungi.

I'm sorry.

Can I bring out some of the stuff that Mugu've made, by the way?

These are some of the

wall panels.

Okay, I mean, lighter than you might imagine.

Yeah.

Okay, so how can we describe this?

It sort of has the, I mean, it's very, yeah, very light.

This nice

ridged surface, how would you say that?

Yeah, I mean well see that I think you can just design.

So it looks like a it looks like a um bar of chocolate.

I did.

I did not imagine that the mushroom came up with that and it wasn't.

Yeah, yeah, yeah, yeah.

But it does show that basically you can make the fungus grow to whatever mold or shape that you want it to.

Absolutely.

So so so fungi are very amorphous and they will grow in whichever direction the food is.

They'll fill a space that you give them.

I mean they feel a little bit like um uh chipboard to a certain extent.

You are presumably not taking good quality wood and turning it into wood shavings in order to do this, right?

This is like scraps and leftovers from other projects.

Oh, absolutely.

Okay.

So that one's actually made from hemp shiv and cotton residue.

Oh, yeah.

But also, what mycelium is made of is fire-resistant, isn't it?

You can set mycelium on fire.

No, so some of the properties of the cell wall of the fungus mean that it is quite fire-resistant, and that's just thanks to the long-chain molecules that it's made up with.

So, there's lots of interesting biochemistry if you're a biochemist, that means that it's very difficult to set this stuff on fire.

Quite useful.

It's almost like the gnome in their hemp house.

The fire protection is going to be

a good thing.

I feel like that's definitely in the pro column rather than the con, that it won't go on fire.

So, it's light, it's shapeable, and you're using waste products that you otherwise wouldn't be getting a use out of.

Yeah, that's that's that's it.

And we think it could last and last and last.

Yeah, it should do.

Fungi, the old, I mean, I'll go back, I'll talk about honey fungus, right?

So, an example of a natural fungus, um, it's the largest organism on Earth, right?

It covers up to three and a half square miles just of mycelium.

And

yeah, well, it's as single as a fungus gets.

But this mycelial network is thought to be between two and a half and eight and a half thousand years old.

So, this stuff lasts.

It's pretty, it's pretty consistent.

Oregon in the USA.

Right, okay, yeah.

Sorry, that's absolutely crazy.

Yeah.

There's an 8,000-year-old single organism that is three kilometers wide.

I mean, this...

Yeah, I think it's bigger than.

Sorry, it's three and a half miles.

Oh, sorry, my bad.

And then it's like eight and a half kilometers or something like that.

And it's eight and a half kilometers wide.

Yeah, and it could be eight and a half thousand years old.

It's incredible.

Like, fungi are just absolutely incredible, and you really have to suspend what you think you know about living things.

Yeah.

So, right, while we've been playing with these samples, we have snuck another person into the studio because we have been joined by Patrick Baptista Pinto, who's the co-founder of a company called Really Clever.

Great name, by the way.

Thank you so much.

Okay, so up until now, we've been talking about sort of making bricks and things by growing mycelium through stuff.

decaying stuff but you're doing something different right so yeah so what we're essentially doing is we help brands and consumers decarbonize their supply chains by being able to offer a material that can displace any plastic or animal derived products so if you can imagine a sneaker or a car seat or a handbag as an example you're making mushroom leather mushroom leather we type we like to call it a biomaterial but we can lean into mushroom leather thank you for for my purposes of today but are we absolutely okay okay how do you make mushroom leather so what we do is we take the stem of the mushroom right so there's three core components let's call it to a mushroom i know you kill me for this uh particular definition but let's say three core components you have the first which is the mycelium the root structure under the ground yeah that's what we've been talking about yeah then you have the stem that protrudes from the ground and then you have the fruit and body that we consume yeah now for decades mushroom farmers have had no use for this stem of the mushroom because there's no nutritional content so what we've been able to do is we've recognized a different classes of compounds and molecules that are responsible for a great feeling material so what these mushroom farming partners does do is they take this waste stream they essentially just compact it synthesize it's basically this liquid, and ship it to our factory.

Get the stems, put them in a blender, send them to you.

Nailed it.

Right.

So, this is one of the core ingredients.

We then introduce some other bio-based ingredients, algal-based inputs, natural latex as an example.

And the output's kind of a viscous cake-like mixture, biopolymer.

So, we basically put this liquid into a tray, put it into an oven, it cools, and it comes out like this.

Oh, wow.

So, you're holding up basically that looks like suede, leather, correct.

It looks like the back of a car seat.

Pervision?

Period.

The feel of it is like it's sort of somewhere between rubber and leather, right?

It's sort of like got the stretchiness and almost plastickiness of rubber,

but then the texture of it across, as you run your hands across it, is very leather-like.

But so you can,

remember, you created a thing that can be used in, I'm trying to go to bags, sofas.

So where would this stuff appear?

Well, what products could this appear in?

So.

as a perfect example.

Okay, there's a trainer.

That's a trainer as an example.

I'm sorry, so

the leather parts of it here, the leather uppers, let's say, they are made of this of this correct so the shoe upper the material is completely um 99 bio based uh and it's gone for all the testing standards not tow you could not tell i'm just gonna say it's just it's just a shoe it's just a shoe it's just a shoe okay but and how durable is it in comparison to leather yeah so in terms of um leather and synthetic so plastic materials it's completely like for like the only difference between leather and ours is is um breathable leather is naturally breathable where our material actually isn't right apart from that it's the same in every context, from price to performance and quality.

So, we are saying there is an increased risk of athletes' foot.

Is that

with this?

Hopefully, not it's completely hydrophobic, so no moisture comes in.

Oh, there's a lot of sweat from the inside.

Yeah,

I'm speaking as a teenage boy, formerly.

It does feel like it's like a patch of leather.

It's just a shoe.

I mean, there's something quite sort of mundane about the output, but I guess that's sort of the point, isn't it?

Really?

Of course, yeah, absolutely.

Yeah, so you're not even thinking of them a second time.

Okay, so these are some of the products that are appearing now, But I bet you didn't think that this discussion could end up in space, but you're wrong, because NASA are working on this as well.

Have a listen to this.

My name is Lynn Rothschild.

I'm a senior scientist at NASA Ames Research Center in California.

And what we're trying to do is use fungi as a building material to build habitats and other structures off-planet, whether in low Earth orbit or on the moon or on Mars.

When you're working in space, a lot of the cost of the mission is really launching off Earth's gravity well.

And so the more that you can take out of what you launch into space, the better.

If you launch something that's biological, you could in principle launch very few and then have them grow off planet with, say, water that's sourced locally on the moon or Mars.

And so this should be able to solve a lot of your up mass problem.

So our initial plans are to develop inflatables that are space hardy.

So, I always sort of imagine one of those jumpy things that kids jump in in the summer.

It can be more of a habitat sort of shape.

And you seed that with the fungal mycelia and maybe some dehydrated wood chips, but you keep this as low mass as possible, you fold it up, and you send it off-planet.

And at that point, once you get there, you push it out the door, you give it some water that's locally sourced, or maybe you've had to bring a little with you, and then the fungi start to grow and to bind these wood chips or whatever you've sent.

Well, we've done prototypes of little tiny cubes.

We've made bigger bricks.

Chris Maurer, the architect that we're primarily working with, has made some structures that are imitating what we think of off-planets.

So a four by four meter dome.

And in my lab, we've also made a little stool that my students have made, which doesn't look like much.

It's one of those things that only a mother could love, and yet it's gone viral on the internet.

In fact, it's gotten to be sort of a classic photo op.

People come to my lab and they want their photograph taken standing on this stool.

Fungi could have a really, really big role ultimately in space exploration with food, with clothing, with structures, and there are probably a lot of things that I'm not even thinking about yet.

Traditionally, I always go with whatever NASA say, but fungi is not catching on.

I wasn't aware that that was a thing, that there was a transatlantic difference between fungi,

fungi, and fungi.

Would you like to see the stool?

I'd like to see the stool, yeah.

She described it as a thing that only a mother could love.

Oh my god, no, that's awful.

It's absolutely dark.

I don't think she's helping with our fungal cat.

I mean, it's certainly got the hint of decaying matter about it.

Phil, can I bring you in this?

This is not dissimilar to what you were talking about,

except that this process will happen in space.

I mean, I haven't quite got my head around how it is that they're actually going to be doing that, unless you can create the right atmospheric conditions for the mycelium to grow.

Right, in terms of temperature, in terms of the amount of water you have.

Yeah, humidity, temperature, the right levels of CO2, access to oxygen.

It may be one of these things which, like a lot of things when it comes to this,

is dependent on being able to extract water there, you know, and being able to use that, which is a whole other...

I mean, it might just be easier to do it in the Sahara.

Do you know what I mean?

Don't bother going to space.

Do you know that?

Much less hard.

And then fly it up in a rocket made of

fungal rocket, an entirely fungal rocket with a mushroom leather dashboard.

So that's where we've landed, then, is it?

So

we've got human houses not yet,

but mushroom rockets and gnome houses on the moon.

Yes, sir.

Essentially, yeah.

I mean, I think that would be quite beautiful if just a gnome sitting on top of a toadsuit on the moon looking back, but with a fishing rod.

Always with the fishing rod.

Realistically then, what are we talking about?

Five, ten years' time, what can we predict mushroom-based products that will be in the home?

Mushroom-based products in the home.

I imagine we're going to see more building materials like we've seen the examples of today.

But I think also we're going to see a big

increase in the number of fungal-based pharmaceuticals and personal care products.

Phil, would you add anything to that list?

Yeah, I'd say that in terms of your interior, you don't have to wait until tomorrow.

They exist now.

You've shown some of those products already.

I think what we will see is greater diversity in the products that we're producing and an increase in the kinds of function that they can perform.

Patrick, what do you reckon?

For me in particular, I believe we will, over the next five to ten years, we'll start seeing a lot more sneakers on the market with no plastic and instead featured kind of mushroom leather or mushroom materials in this context.

But over the longer term, I think the minute we start adopting and adapting the material ready for electrical vehicles i think that will be the big growth sector as well so short-term sneakers fashion longer term automotive and hopefully aerospace and a pair of leather trousers for the midlife uh crisis older man for you i'll do it i'll do a proof of content for you no problem thank you very much you've been absolute pleasure to talk with thank you very much to kaylee field to phil airs and patrick baptisto pinto

I mean, I mean, has it turned you around on the fungal world?

Does this mean I have to eat mushroom risotto risotto now?

Yeah, I mean,

that's the entry level.

I mean, if you're going to live in a house, if you're going to live in a house entirely made of fungal material, wearing your fungal clothes, sitting on a fungal couch, yeah, I mean, it really would be ridiculous if you couldn't eat a risotto at the same time.

All right, I'll concede then.

This house is also in the mood, did I mention?

Subscribe to Curious Cases on BBC Sounds and make sure you've got push notifications turned on and we'll let you know as soon as new episodes are available.

How can a celebration

Japanese tradition of kintsugi, South African Ubuntu philosophy, and many more.

Don't miss something to declare from BBC Radio 4, available now on BBC Sounds.