when first addressing a large and extremely genial French fashion designer disguised as a cartoon Mexican, a straightforward approach seems advisable. So which of Jean Paul Gaultier's catwalk shows has given him the most satisfaction? "The collection I like is the one with the tattoo people - there was a T-shirt of tulle; it looked like it had a tattoo print, but in reality it was billets de banque." It takes Gaultier three or four patient repetitions to establish that he has just said the French for banknotes. His famously improper English actually has its own transparent flow; it's only his native tongue that muddies the waters.

Jean Paul is in the midst of filming his links for Eurotrash, the cheery Channel 4 sleaze-fest whose Friday-night ratings are the envy of many a more reputable production. Gaultier's charming presentational double act with suave Rapido vowel-strangler Antoine de Caunes has established the pair not just as the only two Frenchmen upon whom the bulk of the British populace can be relied to look with favour, but also as a perfect model of gay and heterosexual male friendship. It's just a shame they have to spoil the programme with all those dreary items about toilet museums and silicon-breasted porn stars .

Given that half the fun of Eurotrash comes from its unshockable Gallic presenters' endless amusement at the uptightness of their British chums, Gaultier's attitude to this country is not as one would expect. He first came here, aged 20, in 1972, and found it very much to his taste. "Because there are a lot of conservative and puritan people, when you want to express yourselves by being bad little boys or little girls you do the worst thing with a lot of pleasure and creativity in it. In Paris I felt always it has to be chic, it has to be elegant: in France the fat girls they try to hide it, in England they were all dressed kind of sexy with black lipstick, very much like 'here I am', which I love, you know?"

His own background in suburban Paris is generally supposed to have been quite restrictive. Was that actually the case? "In some ways not. My parents were accountants, but my father was a little, I shouldn't say," a grinning Jean Paul waves his arms to summon up the correct phrase, "not a very good accounter. His head was too much in the air to be an excellent one." For all his father's unreliability with figures, Gaultier junior had a "very good childhood". "My parents loved each other," he affirms, "and I am very pleased of that, because it balanced me a little."

Gaultier's key familial influence, though, was his "extraordinary" grandmother. "She was a faith healer," he explains, "who was also giving massage and beauty advice and playing tarot." Her house was warmer than his parents' home, and the young Jean Paul used to spend a lot of time there. "I could hear what she was saying to her customers - 'oh, you should change your haircut' - and I was realising that by how you dress you can say something." With his trusty sketch book, he began to take an increasingly active interest in his gran's beauty treatments. "I was sketching the heads of the customers - how they were and how they should be."

His first mannequin was an unfortunate teddy bear. "I was doing to that bear everything that was happening at the time. It was the time when Professor Barnard was doing open heart surgery, so I opened the heart of my teddy bear. Also I made the first cone bra for him, because he had no bra ... and I dressed him for the wedding of Fabiola and Baudoin [Belgian royals, the Charles and Di of their day]." Allowed to watch whatever he wanted on the grand-maternal TV, the young Jean Paul eagerly absorbed outside influences - Marilyn Monroe, the Rolling Stones, the Folies Bergere.

Did he have trouble fitting in at school? "I am not Cantona," Gaultier observes modestly. "I did not know very well how to play football. So when there was a match and people would have to say 'Gaultier will be in that team' it was 'ooh, no, no' - they never wanted me. I was completely rejected. But because I was good at drawing, I was accepted for that." Aged only six or seven, Gaultier was busy alleviating the boredom of a lesson by sketching a Folies Bergere girl - complete with feathers - when he was apprehended by an irate teacher. "The institutrice wanted to punish [distinctively rhymed with 'soonish'] me. So she put the picture on my back and made me make a tour of all the different classes to make me ashamed. But in reality it was excellent because it made everybody like me."

Jean Paul Gaultier never had an academic introduction to fashion. It was his drawings that got him in on the ground floor. He sent a selection round Paris fashion houses, and on his 18th birthday he received a phone call from Pierre Cardin, asking him to come and be his assistant. Was that a very formal environment to suddenly find himself in? "Cardin was a crazy man: nothing was very much established with him, so it gave me the idea of everything being possible." Not all of Gaultier's subsequent workplaces would prove so conducive. When he turned up to work for Jean Patou wearing riding boots: "People would say 'where's your horse?' And they were not joking."

Patou's gave him another glimpse of fashion fascism in the form of a model with a binding corset. "I was very shocked when I first saw it," Gaultier remembers. "She said they thought she had too much [he mimes abundant breasts], but my mentality is always that when you are round you should show it and when you are slim you should show it. You have not to be ashamed of yourself." For all the extravagance of his most celebrated designs there is an air of robust common sense about Gaultier that runs counter to the preciousness for which the fashion industry is justly notorious. "I do not like the principle that to be fashionable you always have to hate what you have loved before," he insists. "Like there is some lover you have, and because you have another one you have to hate them. It can happen, of course, but it can be also an accumulation - like a harem!"

Gaultier's creative partnership with Madonna - specifically the sumptuous male harem designs for her Blonde Ambition tour of 1990 - has been well documented, but his encounter with another powerful woman is not such public knowledge. Is it true that he once dressed Imelda Marcos? "Yes. I didn't know at that time exactly who she was, but she had come back from the US with presents for her entourage, she was throwing them into a room and about 30 people were fighting for them." At that time Gaultier (who was in the Philippines for Pierre Cardin) was not yet trained to do fittings, but he did one for the First Lady. "I kept saying 'Raise it here!', 'Raise it here!' And the sewing person had to do it. Imelda looked very bad, but she did not complain - she thought that was how they do it in Paris."

There was a bad time at the start of the Nineties when it looked as though Gaultier might end up in that least desirable of categories, the Eighties leftover. The turn of the decade also brought the awful trauma of his partner of 15 years dying from Aids. But the gently ebullient Gaultier now seems to be working harder than ever. Does he never want to take some time off? "If I stop for one season and there is nothing to present, there are a lot of people who work with me who will be in trouble." That sounds like a bit of a burden. "It is sometimes, but I am usually excited because there is always some new idea and I have to make it done."

In the meantime, Gaultier seems to derive great enjoyment from moonlighting in the salacious world of late-night TV. "I am not an actor," he assured de Caunes when the Eurotrash notion was first mooted, "I can only be myself." As Jean Paul Gaultier struggles manfully to keep a straight face while repeating the line "big fat furry Mexican cock" and simultaneously endeavouring to mount a giant pantomime chicken, there's no getting around the fact that this is a man of rare and captivating dignity.