However, you only have to read (or look at) Briggs' books to realise that here we have an unlikely candidate for festive canonisation. Father Christmas is constantly grumpy at the drudgery that his job entails; after the boy and the snowman go on various magical adventures together - including a trip to see Father Christmas that's in the screen adaptation but not the book - the snowman promptly melts.

Nor does the rest of his work make for much chirpier reading. In (1980), central character Jim Bloggs is thwarted at every turn in his attempts to change career from toilet cleaner to, variously, pirate, artist, highwayman and cowboy. Jim and his wife Hilda return in the indescribably downbeat and tragic (1982), dutifully following useless government advice before the world is annihilated by nuclear armageddon. Even his more light-hearted stories, such as (1977), feature a central character whose job of scaring human beings is, like Father Christmas', actually quite dreary.

But Briggs sees his habitual pessimism as just telling it like it is.

"It's just being realistic. Father Christmas is old, fat, has an awful job, has been doing it for a lifetime, it's night work, it's freezing cold, he's alone all night - who wouldn't be grumpy? And the snowman melts, and nuclear war kills people in thousands. Am I pessimistic or realistic? Both. The light at the end of the tunnel is probably an oncoming train," he says.

"And none of my books are about Christmas, except obliquely - but Christmas always soaks up everything."

Born to working-class parents in southwest London in 1934, Briggs wanted to be a cartoonist from an early age. After spending several years at various art colleges, including London's Slade School of Fine Art, he embarked on a career as a professional illustrator and, to his initial horror, was asked to draw for children's books. He soon realised, though, that illustrating and authoring children's books gave him the freedom to pursue his distinctive vision. He pioneered the graphic novel format, where separate words and pictures had previously been the norm, and made the bold decision to go entirely without words for .

He also moved from works aimed mainly at children, such as and , towards books with more grown-up, often extremely dark themes - but without changing his works' simple picture-book form. looks like a children's book but is about human powerlessness and horrific slaughter; likewise 1984's , a satirical allegory for the Falklands war in which two ridiculous metal monsters wreak havoc fighting over a "sad little island".

But to Briggs, the apparent disconnect between form and content has never been an issue; in fact, his work effortlessly bridges the gap between younger and older audiences precisely because he makes no distinction between them. "You just do what you do the way you want it. I never think about whether a book is for adults or children. Apart from early learning books, 'The cat sat on the mat' and so on. Once a child can read, I can't see the difference."

But then, Briggs says that the audience with which he is most associated remains something of a mystery to him ("I don't know anything much about children: had none myself, never taught in school") - a fairly startling admission from an author whose work is so beloved by so many children.

He has, however, taught young people: for 25 years, from 1961 to 1986, as a part-time tutor of illustration at Brighton School of Art. It's something he misses to this day. "It was good fun. It was inspiring to be among a bunch of young talented people; I learned such a lot. Seeing one of them with rows of colour crayons laid out inspired me to get some myself. This produced , all done in crayon."

He says creating a book without words is "much harder" than writing one with them ("every action has to be depicted, not just mentioned"), and that drawing is actually a far more challenging business than writing generally. "Writing is far easier and quicker than drawing. 'John picked up a mug of tea': writer - job done; illustrator - what does a 60-year-old hand look like? What angle are we seeing it from? What is he wearing? Etc, etc. It's much more of an effort. It's sometimes a drag to think when you've been writing for weeks to have to relive it again and draw it all - months of work."

In addition to child-friendly works such as (1992), about a tiny human who mysteriously appears in a boy's bedroom and starts bossing him around, and (2001), about a young caveman who comes up with various forward-thinking but unpopular inventions, Briggs' later career has also produced the book that he refers to as his favourite among his own works: 1998's . Also the work about which he says he's had the most correspondence from children, it is the life story of the two people who dominate his works more than any others: his parents. They are also the basis for Jim and Hilda Bloggs in and , while a milkman based on his father is the only other person in with whom the main character interacts.

His most famous, successful and resonant work, however, continues to be , which will be performed again in Hong Kong on December 8 and 9. Briggs says he had "no idea at all" when he was writing it that would be so successful. In fact, he admits, he wasn't always such a fan of the animated version. "At first I didn't like the idea - visiting Father Christmas and so on - but the book is 32 pages, as most picture books have to be, with four lots of eight-page sections. Films like that have to be 26 minutes, so more story was needed. I came to like it when I saw it all together."

So he should: it's the work that's installed this least cosy and reassuring of writers as a festive family favourite. You could almost see it as a happy ending - except Briggs doesn't seem to believe in that either.

The Snowman and The Bear