Pinned to the door of Raymond Briggs’s studio is a handwritten sign. “Raymond is not a normal person, signed Connie, 3 years and 6 months”.

“Don’t you think that is extraordinary language for a three-year-old?” he says. “You’d expect her to say something like ‘Raymond is a funny old man’, not use sophisticated ideas like ‘normal’.”

But Connie, now aged 14, was on to something. Raymond Briggs is really not normal. Not so much because of his eccentric collection of Queen Mother jigsaws, or even his legendary grumpiness (he’d just cancelled an interview with Chris Evans, “that ginger-haired git”, when I arrived), but because his devotion to and mastery of “graphic novels” – a much neglected form of art in Britain – has made him very famous, very popular and very wealthy.

No other artist, with the possible exception of Posy Simmonds, is associated with cartoon stories like Briggs, and this winter, as the film of his bestseller The Snowman celebrates its 25th birthday, there is a well-deserved flurry of appreciation going on.

Not only is the film celebrating (the book itself was published nearly 30 years ago), but the hugely popular stage version is enjoying its tenth Christmas. A new production of Fungus the Bogeyman opened last month at the artsdepot theatre in North London and Father Christmas and Father Christmas Goes on Holiday, Briggs’s brilliant cartoon stories of a curmudgeonly, exhausted Santa who prefers his cat and his dog to the millions of children to whom he delivers presents, continue to sell across the generations.

His home in East Sussex, where he has lived since 1967 when he got a job teaching art at Brighton Polytechnic, is a small, square cottage full of light. There is a wonderful depiction of it in Ethel and Ernest, the book published 19 years ago about Briggs’s parents – his father Ernest, a milkman, and mother Ethel, a former housemaid.

In the book Briggs, a long-haired, hippyish young man, is holding his head in his hands after Ethel describes the cottage as “a dump”.

“Dump! Mum! The Government has designated this an AONB – an Area of Outstanding Natural Beauty. It’s official!” he wails.

“Those were her very words,” he says now, smiling grimly. “She stood there in the lane and said, ‘What a dump’. ” Ethel and Ernest, the story of his parents’ life together and therefore of his own early years, is his favourite book. A departure from his usual children’s books, it is remarkable for the fleeting, observant way it captures the attitudes of respectable, working-class postwar Britain. Nick Hornby is quoted as saying that social historians have said a lot less, in many more words than Briggs manages to do in Ethel and Ernest.

I can’t imagine what words Ethel would have used to describe the state of the cottage today, in all its chaotic splendour, which one admiring neighbour insists should be “preserved for the nation”.

The walls are crawling with pictures, photographs, leaflets, sketches, trays, badges and mementos. Books are piled everywhere – Magnum photos, Antony Beevor’s Stalingrad – and there are two life-size models, one in the sitting room of Briggs himself as a very old man stooped over a Zimmer frame with his flies undone and everything on view. The Queen Mother jigsaws line the staircase (“I pick them up in junk shops,” he says).

Ethel and Ernest died in 1971, a few months apart. By then, Briggs had won the Kate Greenaway medal for distinguished illustration in a children’s book. (He won it again in 1973 for Father Christmas). Briggs was already well established, and so she and Ernest died safe in the knowledge that their son’s unconventional career choice was working out. “They were baffled by it [his decision to go to art school] because it was completely outside their comprehension. None of our family had ever gone to further education, let alone art school,” he says. Then, in 1973, Briggs’s wife Jean, who suffered from schizophrenia, died of leukaemia. “Yes, that was a jolly time,” he says.

Because of Jean’s illness, Briggs never had children of his own (another detail to emerge in Ethel and Ernest), but for the past 30-odd years he has been a surrogate father to the two, now grown-up, children of his partner Liz. (As children in the 1970s they had walk-on, or sleep-on, parts in Father Christmas). Liz lives in the same village. They never moved in with each other as it wasn’t practical, but are, apart from that small detail, as settled as any couple could hope to be, and are very involved with Liz’s three grandchildren, including the perceptive Connie, who live near by.

Death is the subject of Time for Lights Out, Briggs’s next book, “if I ever finish it, if I get to the end before the end gets to me”.

“It’s a great, enormous, endless book about old age and death which I’ve been working on for two or more years and still haven’t got anywhere near the end of. It just goes rambling on,” he says. “It’s different from what I have done before, it’s all in pencil, black and white, it isn’t in strip, though there are bits of strip in it. It’s difficult to describe, really – it’s an amorphous mess at the moment.”

Each of Briggs’s bestselling books has been the product of months of painstaking work – the Father Christmas books and The Snowman took 18 months or so to complete, while Ethel and Ernest was a three-year labour of love.

To use his own words, the business of putting together a strip cartoon book is “fiddle-arsing beyond belief”.

“It’s rather like making a film. You have to write the script, then become the director. People don’t realise how complicated it is. You have to decide who is coming in from the left, who from the right. Who speaks first – the maddening thing is that the person on the left always has to speak first, which is often very awkward.

“Then you have to become the set designer, and ask ‘Where are they in this scene?’ Is it a kitchen? Is it the sitting room? What is the view from the window? Then you become the lighting person. Is it evening? Have they got any artificial light on yet? What’s the light like outside? Then you are the costume designer. What are they wearing? What did a woman’s pinny look like in the 1930s?

“Then, when the ‘film’ is finished you have to put that to one side and become a book designer – do the typography, lay out the pagination, design the number of pages . . . in film or theatre you would have hundreds of people doing this for you. But you have to do the whole bloody thing yourself.”

Briggs even remembers delivering the artwork for Father Christmas (painted on boards) to his publishers in a big wheelie suitcase.

Fiddle-arsing indeed. Perhaps that’s why so few other British authors have managed to produce graphic novels with the same level of appeal as Briggs’s. He is more inclined to think that there is snobbery at play. Unlike in France, say, or Japan where la bande dessinée and mangaare respected art forms, there is a much weaker tradition in the UK.

“All the subsidies go to opera,” says Briggs. “Because the people who work at the Treasury are opera fans. Next comes ‘the theatah!’ ” Cartoons languish somewhere near the bottom of the pile.

Briggs still recalls how the head of Wimbledon Art College, which he attended aged 15, sneered at his professed desire to do cartoons. He was forced to do fine art instead, which although he was obviously good at, was never what he wanted to do.

Now, though, although he shrugs off any suggestion of greatness, Briggs has given respectability to “graphic novels”. At the age of 73 he has become the grand old man of the genre. He shows me a soon-to-be-published “graphic novel” from a new author about the animals in Baghdad zoo that escaped during the war – The Pride of Baghdad. The publishers have sent it to him for an endorsement. Briggs is enthusiastic.

If Briggs sounds morose when describing Time for Lights Out, he nevertheless seems to be enjoying his seventies. Unlike Father Christmas, who clearly resents having to do his job past retirement age (“blooming Christmas, blooming snow, blooming chimneys, blooming soot”), life seems pretty good – although he lapses into Father Christmas mode when he describes the publicity round that he has been booked on to celebrate The Snowman’s anniversary.

“When you get old, everyday life takes over,” he says. “You seem to spend all day doing everyday life things – shopping, going to the building society, going to the chemist and all that. Then, when you get back, it’s time to walk the dog again. Before you know where you are it’s 4 o’clock and you haven’t started. It happens time and time again, it’s maddening.”

Again, I can’t help thinking of Father Christmas and Fungus the Bogeyman, both characters who are funny and appealing because of the very “real lifeness” of their existences.

By the time I leave, it’s dark outside and the fields look decidedly frosty. Although Briggs never set out to be associated with Christmas, it seems an appropriate time to have visited. He says goodbye from the top half of the stable door that is his front door and as I turn to wave, I’m half expecting him to say: “Happy blooming Christmas to you too.”

The Snowman, Channel 4, Christmas Eve, 1.50pm

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