Every small boy wanted to be a steam engine driver when they grew up in the old days, including me. There's something very special about them - the noise, the smell, the steam coming out everywhere.

In 1941, the BBC was setting up local, low-powered transmitters that were switched off if there was an air raid so they couldn't be used by German planes to navigate. As a 'youth in training,' my job was to switch the transmitter on in the mornings and off at night, and to check that it, and the feeder land lines, were working.

I worked on 'Blue Peter' and 'Tonight' and lots of TV plays, filmed people like Rudolf Nureyev and Ted Heath, and ended up a senior cameraman with my own crew. I'd had my first short story published in 1947, and when my writing really started to take off I decided to go freelance, and eventually left the BBC in 1965.

The great advantage of having a bear as a central character is that he can combine the innocence of a child with the sophistication of an adult.