I was prepared to hear - as any of you would have been by that stage - many odd things about Si and Dave, the most successful bearded motorcycling culinary experts the planet has known. Tales of broken bikes in the desert, and black pudding made from dog's blood; of beards and camshafts and broken bones and exotic stomach problems in flyblown lands; and earth-ovens and salted lamb and seven things to do with paprika before breakfast. What I wasn't quite ready for, despite a day of surprises, was hearing how they met.

'How we first met? Yeah, easy - it was on the set of a Catherine Cookson mini-series. Anyway, this stuff's nuoc cham, a lovely mild Vietnamese dipping sauce, much gentler than the Thai version, and...'

And Si, or perhaps it's Dave, is off on one again, talking 13 to the dozen as he fine-slices the duck, and Dave, or perhaps Si, picks up the tale as he crouches over the rice paper. And there is much swapping and stealing of titbits from the other's side, and laughter, and explosions of approbation, often involving the somehow completely inoffensive adjective 'fooking', and you suddenly understand the tremendous symbiosis which could make them one of next year's most unlikely TV successes; and then you get to sit down with them and eat a fooking delicious meal.

The 'Hairy Bikers' is not their choice of moniker but they don't really mind too much and there's nothing technically wrong with it, because two of the many things that Dave Myers and Simon King share are being a) hairy, and b) a biker. They also share a love of food and travel. The night before I met the pair together, at Dave's house on the gorgeous frozen windswept Roa Island, off Barrow-in-Furness, Dave had taken me for a pint and explained, simply, 'We were mates, and we liked to get on our bikes and go looking for great food, but work on both sides kept getting in the way. We just sat down one night, not that long ago, and said: "Tell you what a great life would be, that would be one in which we could just ride bikes, cook food and talk bollocks."

'Then all we had to do was see if we could somehow make a living out of it.' He explodes with laughter. 'Sometimes, most of the time, I can't quite believe it, believe that we have. It's been a big surprise. It's been a great ride.'

So: hairy they are, and bikers they certainly are, their machines of choice being a BMW GSI200R for Si and, for Dave, that rare beast a Hesketh V-1000, one of the most beautiful British bikes ever made and also one of the heaviest, as we discover when it suddenly refuses to start after the photoshoot and it pretty much takes four of us, with much sweat and exuberant use of the word 'fook', to push it home.

What they're not is any old hairy bikers. Both have spent years working in film and television. Dave, after a spell in the furnaces of Barrow, became a highly rated make-up and prosthetics man (Life and Loves of a She-Devil was one of his, though he faux-cringes now at the Eighties technology). Si was a sometime first assistant director, and more recently a location manager: his last job was the latest Harry Potter, though he's keen to stress the job can be a good deal less glamorous than it certainly sounds, involving a stupendous amount of paperwork and smatterings of recalcitrant locals.

As a result, they were better placed than many simple hairy bikers might have been to develop their idea, go to people rated inside the industry - in this case director John Stroud and producer Vikram Jayanti - and get the go-ahead for a pilot.

They delivered the results of their first trip, a roary jaunt round the delicacies of Portugal, on Christmas Eve, and the pilot programme, which went out in the first week of January, was one of those word-of-mouth things that people still remember seeing and loving: that night's showing won and kept an unexpected audience of over three million. It was clear that their northernness, lack of pretension, blistering good humour and strong friendship waltzed right into the living-room, and that the format they had accidentally hit on - part travel, part cookery, part adventure, part comedy, and all of it with very big bikes - was an extremely happy hybrid. A whole series was commissioned, and starts on BBC2 early in the New Year.

And they can, seriously, cook. 'We're not professional chefs,' explains Si, 'but we just look for the right ingredients, new or ancient recipes, things we just get excited about, and work at it, till it works.' The kitchen in Dave's home may have three heavy bikes leaning outside, and a book of tide-tables open by the sink - he sails a catamaran - but there is also a wall shelf weeping under the weight of some very serious cookbookery; and when the two of them lumber in, still wheezing from their Hesketh exertions, and remove their helmets, they are transformed. Big bunches of biker fingers are ungloved and warmed and washed and de-oiled, and Dave shows great delicacy with the rice-paper, and Si looms opposite like Hagrid with a garlic-press, doing tender things to ginger and shallots, as the pair turn out a fast succession of Vietnamese crystal spring rolls. Then some red-snapper fishcakes with chilli and green beans; and pho (pronounced fir), a great beef-bone broth with black cardamom and cinnamon and star anise; and a host of other delights rich in galangal and turmeric and the like, and while Si's busy chopping and frying, Dave takes a second to open a bottle of rosé and simply enthuse.

'The great thing about this country now is that you can source all these things pretty locally. Everything here, everything we're cooking for you, I bought yesterday from a girl in the market in Barrow. Kingie [Simon] lives in Newcastle, so all he has to do is go to Stowe Street, their version of Chinatown.'

Si's father, who died when he was eight, was in the Merchant Navy, he explains, and was in the habit of bringing back exotic foods from his travels, kit-bag bulging with garlic and spices and paprika. It wasn't exactly the kind of food his mum, brought up in a pit village, was best used to cooking with, but she, Si and his elder brother and sister took happily to experimenting. 'There was always the smell of odd spices. Neighbours used to call out, "Eee, Stella, what's that, it stinks," but mam was really into it.' Similarly, Dave, across on the other coast, grew up knowing he liked stuff which might taste marginally more interesting than chip butties, and finding out that he was rather good at putting it together. When the pair met that day at work, talk turned of course to bikes, and then to cooking, and they disappeared off with Si's wife and children to Huntly, in Aberdeenshire, where Dave also had an antiques business; and cooked for each other - a Thai green curry, and some Gloucester Old Spot Pig with five-spice and jasmine rice - and drank together, and something fine was born.

They spent the next few years getting away whenever they could, fishing and biking and exploring and cooking by the roadside. 'Our panniers were always filled with, well... pans,' says Dave. 'There weren't any room for clothes. We must have stunk every time we came home; lovely for the wife and girlfriend.' Today, when we meet, is four days after their latest trip, to Vietnam (hence the winning showing-off of their newly discovered dishes). Nowadays their trips are further afield, and they have a film crew travelling with them all the time, and marginally cleaner clothes: but they still cook by the side of the road when they can. The forthcoming series has them biking and baking their way through Transylvania, Namibia, Turkey, Mexico, Ireland and others: laughing and squealing with naked pain in Turkish baths, and making the perfect doner, the best cuts going squashed together with some finest lambs'-tail fat - 'just no relation to what you get late on a Geordie night out,' recalls Si, almost salivating. 'Not even close. It were fooking wonderful' - and doing exciting things such as digging an earth oven high above a river in Namibia, cooking a leg of lamb for three hours and then savouring its perfection as the sun sank behind the silhouette of their bikes, the wine came out and, below, a line of elephants came to drink. 'And they pay you for this, man!' says Dave.

It's not all fun and games. Actually that's wrong, pretty much it is; but they do do their work. Each filmed trip is preceded by a two-week recce to find the most interesting stops, and much work in books and on the net; and each recipe for their forthcoming Hairy Bikers Cookbook (to be published by Penguin in the spring) is diligently and scrupulously tested, usually in Dave's kitchen, before being wolfed.

What they would seem to bring to the world of cookery is, essentially, a questing enthusiasm. They don't just want to eat - well, they do - but they also want to know the history of the area, why some foods have changed, why geopolitics made one spice more prevalent here than there, why this or that recipe might have been fine once but needs updating - there's a fine brief rant during our lunch from Si about Portuguese bacalhau, the national dish of salt cod, which he argues cogently shouldn't be so revered in the days of refrigeration.

Their tastes are what you might describe as the opposite of picky. Outside, they have a slew of game which is heavy and bloody and hairy and feathery; you might think twice before offering it up on (say) Delia's immaculate doorstep. But these boys know exactly what to do with it and are looking forward to hanging and plucking, and eating, what they've had draped round their necks for two hours. Their enthusiasm to try anything - the more eclectic the better - is, I assume, much of what won them the series; and in a perfect world it would translate into a new enthusiasm, for new things, in Britain. Look at us, they seem to say: we're working-class Northerners who love our food tasty and have learnt how to find good new stuff and cook it, and here man, we'll show you how to do it, and by the way it's fooking great.

It's a far and refreshing cry from the worst excesses of foodie London, with its gold leaf and foams and pithiviers and celebrity openings and Michelin bitching. They know a little about all that, and are terribly kind to Rick Stein and, in fact, to Jamie Oliver - Si's five-year-old son is diabetic, and school meals used to be a nightmare until their transformation last year - but they are also pleasantly unreconstructed when I ask about Nigella's recipes; there are a couple of naughty schoolboy grins, and the replies come along the lines of 'never mind the recipes'.

And this whole wider story is not, I suspect, just about food, terribly moreish though it was that day. It's about a couple of long-term mates who were good at things and suddenly had the guts, the guts so few of us employ, to say: 'Actually, what do we really want to do in life? Yeah, me too. Right. Let's do it.' And I get a tiny glimpse of the steel necessary to take the gamble when I suggest, half-joking, that the one minor drawback to such sudden, lovely success is that they are now hidebound in not being able to shave, because of the TV image.

Si looks at me carefully, and the laughter stops for a second. 'Oh, I don't know about that,' he says, quietly. 'We sort of tend to do just what we want. '

· The Hairy Bikers starts on BBC2 in January