This year, Paddington Bear is 50, though he doesn't look a day older than 7. To mark the occasion, his creator, Michael Bond, 82, has written the first full-length Paddington book in nearly 30 years - extracted last Saturday in The Times Magazine. But how did the marmalade-addicted bear from darkest Peru come to look the way he does? It began, in a rather haphazard sort of way, with a longdistance relationship between an author and his illustrator, back in the late 1950s.

Once the publishers had accepted Bond's first story, an artist was needed to bring Paddington to life. Peggy Fortnum, an illustrator who lived - and still lives - in West Mersey, Essex, was suggested. Bond remembers: “It was all done very independently. Peggy took herself off to the zoo and drew a bear from life. She presented the drawings to Collins. They liked them. And so did I. They were quite sketchy, but they captured Paddington's character completely - those sketchy drawings were of a living, breathing creature, with the spirit of Paddington about them: his incurable optimism, his gullibility.

“It was all done long-distance. There was no correspondence about how it should look. We never had any disagreements. I always wanted him to be a real bear. If I'd known Winnie-the-Pooh as a child, which I didn't, things might have been quite different. He might have become a toy bear.”

Peggy Fortnum illustrated that first novel, and subsequent novels in the series, but by the 1970s, the publishers had decided to capitalise on Paddington's appeal with picture books for younger children. The illustrator Fred Banbery illustrated six of these, showing us a world of Paddington bear that was much more detailed than had ever been seen before. Then, in 1975, FilmFair transferred Paddington to the small screen, and Ivor Wood came up with a puppet version of Paddington from which, in the late 1970s, he developed his own strip cartoon for the London Evening News.

In the 1980s, David McKee drew a further series of picture books for young readers in a smaller and more chewable format. And so Paddington has gone on and on, ever changing, ever remaining the same.

Bond was just doodling really when he wrote those first stories. He'd bought a small bear for his wife as a Christmas stocking filler, and it had become quite a member of the family. “There was a blank sheet of paper in the typewriter, and you know how much a writer hates the sight of a blank sheet of paper. Well, I jotted a few words down. I had no particular intention of writing any kind of a book, let alone a children's book. We had no children then. All I had was this little voice inside me as I wrote, telling me whether something was right or wrong, and you tend to ignore that at your peril.”

He showed the episode to his wife, and she liked it, so he went on, day by day. The story was full of local characters, local detail, as the early illustrations testify - the stall holders in the Portobello Road, the people from the local launderette. Paddington was a real bear, dressed up in the sort of clothes that Bond thought were fashionable then: a blue duffel coat, a bush hat...

Fortnum, now 90, remembers the start of her relationship with Paddington with fondness. “I went off to London Zoo, and used a real Malayan bear as a model. I always saw Paddington as a real being. You see, I don't like whimsy or sentiment. This bear had character. I felt a real rapport with this brainless innocent who always came out on top.

“I think I was chosen because I had a facility with pen-and-ink drawing and this is what the Paddington drawings were, essentially, in the beginning, the ones inside the book, with added colour for the jacket illustration. I had first started illustrating in the 1940s, which was the golden age of pen-and-ink work. It was too expensive to use colour inside a book then. It was reserved exclusively for the jacket.”

For the past ten years the Paddington books have been illustrated by Bob Alley, an American who lives in Rhode Island. Alley was chosen to do the book because, like Fortnum, he was essentially a pen-and-ink artist.

“The difference with picture books is that they need a fuller and more elaborated world in which to place the bear, and so there has to be more detail,” Alley says. “Children have to be able to point to particular things. Of course, some things have to remain the same, always - Paddington's dress code, for example: wellingtons, blue duffel coat, big hat - these have to remain consistent. In other respects, and as Michael himself recognises, it is important to keep it up to the minute. The stories need to look current. It's quite a responsibility drawing a character who is so much a part of everyone's world.”

This is certainly true of the new book, Bond's first full-length novel about the character in 30 years, Paddington Here and Now. This includes many more drawings than usual, and one of them is of the London Eye, although there isn't one of the stretch limo that also figures in the book. Alley laughs that he sketched one but it wasn't used.

Has the appearance of Paddington himself changed significantly? Alley says: “Well, Peggy used a wonderful variety of penwork. It was very loose and very fluid. Mine is a little stiffer, and a little more detailed. The character remains the same, but the illustrator's point of view is necessarily slightly differently rendered, slightly twisted.”

The relationship with Bond is much more hands-on too. “I had long discussions with Michael about the redesign of Paddington station, and especially where the left luggage office is these days. Michael was very keen to ensure that the drawings incorporated the new design for the station.”

“Paddington has a lot of my father in him,” says Bond, who still lives within easy reach of Paddington station, by the canal in Maida Vale, West London. “Like Paddington himself, my father - a civil servant - was always very polite, and he always read the small print. I remember that when we used to go on holiday as a family to the Isle of Wight, he'd keep his hat on in the sea, trousers rolled up above his ankles, just in case he met anybody.

“Like Mr Brown, he was also a rather cautious man. Mr Brown is worried about taking Paddington home. My father would have responded like that, too, whereas my mother would have whisked him off straight away. They were both very kind people. The world is rather different now,” he sighs.

Bits of Paddington are to do with the Second World War, too. “We used to see newsreels at the local cinema,” Bond says, “and I so much remember all those poor people pushing their belongings in front of them in prams, or carrying battered old suitcases a bit like Paddington's. And then there were all those people, refugees, who used to arrive in Reading from Paddington station with name tags around their necks - that's just how Paddington himself arrived from his Aunt Lucy's in darkest Peru, with a name tag around his neck, except that his said: ‘PLEASE LOOK AFTER THIS BEAR THANK YOU'.”

Paddington, old or new, is enduringly intertwined with Bond. “Well, you take your characters with you,” he says. “As an author, one is never alone. And why a bear? Well, I think you can tell bears all your secrets. They always seem to have such a wise expression on their faces. I might be a bear in my next life.”

Paddington Here and Now is published by HarperCollins on June 2 and is available from BooksFirst, priced £8.50 (RRP £9.99), free p&p, on 0870 1608080 or timesonline.co.uk/ booksfirst. The audio book, produced by Peter Rinne, is available from the same date

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