By the end of the act, Rory is down to his underpants. On some wacky pretext or other, his chef's white hat, check trousers and t-shirt have either fallen, been ripped away or snatched off him, and for the last manic minutes of his performance he's sliding round the stage in nothing but a pair of white briefs. Not that you can really see them, because by then Rory is pretty much coated all over in Yorkshire pudding batter, and his skimpy underwear is almost indistinguishable beneath the glistening mixture of flour, eggs, and milk.

Rory is one half of a travelling slapstick duo, 'The Cook-Ups', and tonight he and his comedy partner, Steve, are playing a pub in St. Austell, Cornwall. There's enthusiastic applause from the small audience when the pair - suddenly a bit winded and de-energised - take quick, modest bows before turning to pick paths off the now treacherously slippery tiny stage, but I've been following Rory and Steve around for a couple of weeks, and believe that if the audience had any notion of the gruelling work that lies behind their act, or the level of discomfort the two of them are prepared to endure, they'd be giving them a howling ovation and a cascade of bouquets.

Rory and Steve's selling point is simple. They'll play anywhere. They're willing to perform one-night stands in any venue in Great Britain. The problem is their act is quite astonishingly messy, using real flour and real eggs which they mix together in front of our eyes, and then assault one another with in an escalating tit-for-tat routine. Flour-paste is probably the hardest to remove of all the customary slapstick substances, and by the end of the sketch both are splattered in the stuff, yet in many of the venues the pair work in there isn't a shower. So the two comedians regularly face a long journey back to London in their Transit, sitting in cold, wet, sticky clothes, with the much needed hot bath as much as three, four, or even five hours away.

'Why do you do it, Rory?' I ask him.

It's the night they're at St. Austell, and the fourth time I've travelled with them. By some measure this pub has been the meanest venue I've seen them operate in so far (although according to them it's way off being the worst). The only place I'd previously watched them cope without a shower was a working men's club in Boston, Lincolnshire, yet there they'd been given a room to themselves with a basin, so that after their act they could at least strip off completely and wash away the worst till they were comfortable. Here in the Cornish pub there's neither a shower nor privacy backstage - just a single tiny basin in a corridor beside the staff loo. And there's the prospect a long, cold night-time drive back up the A303 still covered in gunge.

'Audiences shouldn't be deprived of seeing some wild slapstick just because the facilities aren't great for the performers,' Rory says. 'Steve and I believe in putting on the same show wherever we are. Then afterwards figure out how we cope with getting cleaned.'

I'd been amazed that even when they'd seen the inadequate conditions backstage here Rory and Steve hadn't modified their usual routine. Surely, I'd thought, they're not going to do the gag where Steve pours a cup of dry flour down the front of Rory's underpants, followed by two cups of milk - there's no way the poor man could ever get clean. But, oh yes - they did. If Rory is having a hard time of it now, he's putting on a good display of stoicism.

'It was drummed into us at Slapstick School,' he says. 'Our job is to entertain, and our personal comfort shouldn't come into it.'

Rory and Steve first met at The National Academy for Training Slapstick Performers - the college in Harrow often known as the Slapstick School. Steve was a mature student; Rory had only just finished his A-Levels. Despite their seven year age difference it was immediately clear they'd make a great comedy partnership. They're a comically ill-matched pair - one small and bossy, the other large and dumb, and their act is a classic. Steve plays the martinet master chef instructing Rory, his dim apprentice, on how to make batter.

Now 33, Steve is short and slender with thinning ginger hair, and exudes a bristling energy. It's just him on stage at the start, and all he does is mix up a bowl of batter (later destined to poured in its entirety over Rory's head), yet the finicky precision with which he measures the flour, breaks the eggs, and dribbles in the milk nails his persona as a petty perfectionist. It's a small masterpiece of comic acting.

Rory, in contrast, is tall, broad and lumbering. Off stage you'd describe him as nice looking, but in character his expression is convincingly gormless as he continually fails to grasp Steve's simplest instructions to the latter's exasperation. They both get messed up in their vicious paste-fight, but since he finishes up practically naked, it's Rory who appears to come off worst.

After their show at St. Austell I get to see the price he can often pay to earn his laughs. I've just watched him rinsing his reddened eyes, and scratching away with a comb at the globules of gluten that cling tenaciously to the hairs on the back of his arms. He'd tried to scrape off the batter from his chest hair with fistfuls of paper roll, and I've caught him quickly scooping as much of the mixture as he can out of his pubes. But the bar staff passes by the whole time, so he's not even had a chance to take off his sticky pants, and because he's now needed to help with the clean-up, Rory's given up on achieving a decent wash and resorted to pulling on a nylon boiler-suit over the top of them. It must feel completely disgusting.

He returns to the stage area where Steve - also now boiler-suited over his barely washed body - is carefully pulling away the sheeting they'd put down to protect the floor. The third member of the team, Mikey, takes the lead. He's a genial, capable man in his late twenties, and acts as their roadie, stage manager, sound operator, lighting engineer, and driver. Together they separate out the dirtied props that need to be kept and washed from the stuff that can be chucked, carefully check for spills everywhere inside the pub, and then start hauling all the gear out to their Transit van. There's a wait before they're paid (in cash, of course), and ninety minutes after the act was over they're at last free to go. It's ten to midnight.

Rory and Steve place newspaper to sit on before they belt themselves in.

'Oh no,' Rory sighs, 'I can feel it oozing round my bum.'

It's the closest I ever hear him come to complaining.

'No worries,' Mikey laughs, '- just two hundred and twenty miles and we're home.'

They've been doing this continuously as their profession since they graduated three years ago. Rory is forever quoting - and impersonating - the college's principal, the renowned ex-comedy stuntman, Graham Weir.

'The Boss used to tell us, "Slapstick performers trade in their rights to comfort and dignity".'

If Weir knows what these two alumni are up to now, then he should be proud of them. They embody his teaching - their work consumes their lives. As I've discovered, their fifteen minute act can easily expand into a fifteen hour day. Tonight they'll head first to the railway arch in north-west London that they've acquired as a store-room for their props, and there - in the early hours - they'll unload the van, and in the yard outside power-hose the stuff that needs washing immediately, like the portable table that features in the act, before the flour-paste on it dries rock hard. They'll chuck their costumes into the washing machine, and then Mikey will run them to their separate flats, which fortunately are not too far away.

After far less sleep than they need, they'll meet tomorrow back at the arch, and the business of getting ready for another show will start all over again - laundering and sorting out clean costumes, loading the props onto the van, going to the cash-and-carry for the flour and eggs, the hardware store for the tape and plastic. (The 'milk' they use on stage is actually a suspension of cornflour and water - I notice they give the cartons a crafty shake before they pour it - 'Not necessarily cheaper,' Rory tells me, '- but a whole lot less smelly when you're driving back unwashed on a hot night'). And depending on where they're booked they'll probably need to be on the road by mid-afternoon, well before rush hour. They prefer to be at a venue about three hours before they're due on stage. It can take all that while to sort out where to tape down the protective sheeting.

What with the price of diesel, the payments on the lock-up and the van, and the cost of all the tape, plastic, and gunge they get through, their overheads eat into the modest amount they're able to charge as a fee. They need to get six bookings a week to earn a comfortable wage, yet when they do it exhausts them.

'Last summer we once worked thirteen nights in a row, and we ended up like zombies,' Rory says.

He looks tired and a bit shivery now as we pull in for a break at Amesbury Services. It's almost three in the morning. The lady serving his all-day breakfast gives his batter-encrusted hair a funny look.

'How come,' I ask Rory when we're seated, '- that you end up stripped, yet Steve here only drops his trousers for a few moments?'

It's a neat gag when it happens. Rory has blinded Steve by sloshing a cup of milk into his partner's face and then blowing a pile of flour after it, and as Steve gropes his way forward, Rory leans round from behind him to undo his trousers, and when they drop to his ankles Steve trips and falls backwards, landing bottom first onto a plate of sticky suet.

'Listen,' Rory replies, '- we'd need an X-rating if the crowd clocked Steve's monster packet for any longer.'

It's true. For a slightly built man, Steve boasts a disproportionately large bulge. It gets targeted when Rory pours a pint of the batter mixture down Steve's front as he remains sitting, splay-legged and de-bagged, but from then on Steve keeps trying to haul his trousers up, so you only get glimpses of his messed-up crotch.

'Though you're not so shy,' I say to Rory.

'Well, let's face it,' he offers without prompting, '- I've got a tiny cock and a fat bum, so why not use them to get laughs?'

I'm glad he's brought this up and not me. Apart from the anarchic amount of mess they create on stage, the other memory-imprinting feature of The Cook-Ups' act is Rory's frankly weird physique. His top half is the build of a Rugby player - deep-chested, broad-shouldered - but below the waist he's unusually wide across the hips, and while his admittedly rather small package perhaps might not register with an audience, his large backside unquestionably does. And yet he's brave enough to draw maximum attention to it. I'd suspected that he gets as much of a thrill from the 'Eugh!' reaction from the crowd as he does from straightforward laughs - like the moment when he's lying on his back and allows Steve, who's standing above him, to drop a cracked egg into his open mouth, or when Steve holds his head right down in the accumulated paste and wipes his face back and forth through it like a dishrag - but then I realised Rory also enjoys the response his exposed body gets. When Steve first forces his head onto the floor he's only in those tiny underpants, and his back is towards the audience, so we get an unmediated view of the vast sideways expanse of his upturned posterior (dead centrally onto which Steve then splats a plate of thick flour-paste), but many members of the audience are turning to one another, drop-jawed, to exchange 'Oh my God!' expressions. The communal reaction seems to be: 'Just look at the arse on that!' - and Rory seems to relish it.

He's a true clown. He sees it as part of his job to suffer nightly humiliation and genuine discomfort. For the gig tonight he's finally dropped outside his Kilburn flat at six fifteen in the morning, and - more than eight hours after he first had a jug of flour paste poured down inside them - he'll at last be able to take off his gunge-y underpants and get properly cleaned up.

It'll be okay this evening - apparently there's a shower at the conference suite at Hinckley where they're the cabaret for an office outing, and tomorrow night at a gay club in Chepstow the manager has said they can use the bathroom in his flat upstairs, but they know that the pub they're playing in Selby on Saturday only has a sink behind the door marked 'Private', so once again Rory will be facing a four hour van ride back to town still covered in congealing paste beneath his clammy overalls.

'Ah well,' he shrugs, '- it's what you have to do, isn't it?'