If you want to draw Paddington, you have to put yourself inside his head,' says Bob Alley, with a chuckle. As the man who has been illustrating the late Michael Bond's books for more than 20 years, under the name RW Alley, the 62-year-old can perform this act of cranial transference better than pretty much anyone else in the world.

'Paddington is honest, he's forthright and he's optimistic because he always sees the good in everybody,' Alley says. 'He doesn't even think ill of [his next door neighbour] Mr Curry, who is just a mean, mean old man. He always thinks he can turn any situation with Mr Curry into something good. It's that sort of kindness that partly explains why Paddington is still so popular. People would like to live in a world as kind as that.'

Just how much affection the world feels towards Paddington has become clear in the past few years. A film adaptation starring Hugh Bonneville, Sally Hawkins and a computer-generated bear with the voice of Ben Whishaw was a surprise box-office hit in 2014, while the sequel, in which Paddington was (unjustly) slung in prison and then staged an escape in a hot-air balloon with an inmate called Knuckles, grossed more than £175 million worldwide.