Mr Benn is regularly described as a ‘cult’ children’s TV show, yet mention his name to pretty much anyone who grew up in Britain from the 1970s onwards and the chances are you’ll receive both instant recognition and a gasp of glee.

An everyday figure, dressed in a suit and bowler hat, Mr Benn accessed a steady stream of adventures via his local fancy dress shop, which served as a portal to other worlds. By donning the outfit of a knight, he found himself travelling back in time to a king’s court, while that of a pirate would see him cast out to sea.

While he is probably most famous for the series of animations that the BBC aired on rotation for decades from the early 1970s onwards, the character first appeared in book form, when illustrator and author David McKee decided to create a children’s story about knights. “It wasn’t anything to do with a series or costume shop idea, I was more interested in doing a story about a knight in an army,” he says on the phone from his home in France.

“I was cartooning for newspapers and things and knights were a subject that came up every now and again,” he continues. “So I did the book and then the front and back, the costume shop business and the reality thing, it developed from inside outwards. I didn’t have the idea and just write it – I wrote the red knight bit and then it changed. As books always do, they change while you’re working on them, right up to the end in fact.”

The book turned into the animations we love so much after the BBC approached McKee to create a programme for the Watch With Mother series. “We’d just bought a television I think at that point and the best programmes were the ones for children at midday,” he recalls. “Trumpton and that kind of stuff. I had an idea about a fort, because I thought the enclosed life of a fort, you could have everything within that… But I talked about that with the BBC and they said ‘well no, they didn’t really fancy that as an idea’. And then I mentioned Mr Benn.”

McKee wrote the series and then went about finding someone to animate it, initially approaching John Ryan, who created Pugwash. “John was very nice,” he says, “but his sort of style wasn’t what I wanted.

“So in the end it was really just a case of just jumping in. I knew the principles of making [animation]. This is the sort of thing that would never happen now. Everything’s much more controlled, there are many more committees.

“It was terrific that they had enough faith to let me just go off and do it, really…. But when you do that, when you let someone run like that you get much more of a voice. When it’s committee made – everybody has to say something, obviously, to justify their place in the committee and that dilutes it a bit, you lose individuality.”

McKee worked alongside his assistant Ian Lawless to create the films. “I would draw it mostly, and then he would colour it. Some scenes I would colour as well, but it was not done in the machine. It was very time-consuming and a lot of drawings. I did a lot of detailed drawings and used a lot of camera movement. There’s lots of pans and zooms and quick cuts.”

Ray Brooks provided the voiceover. “I wanted it to voice it myself to start with,” remembers McKee, “but the BBC said ‘well, you can’t do it all’.”

It is slightly surprising to discover only 13 stories were ever made as animations in the original series (with a 14th made in 2005). Perhaps because the BBC repeated them so often over the decades it now seems like more. As well as their whimsical charm, what characterises the series is a sense of morality, with Mr Benn usually taking the role of peacemaker or problem-solver in every scenario he finds himself.

“I was brought up with a moral background,” says McKee. “My parents were very strict, in a way, about everything being correct. Also I liked fables, and I even liked the parables in the Bible that they used to read at school…. I guess the moral side just comes out automatically if those are your influences.”

There is one Mr Benn story that appeared only as a book, the story of Mr Benn entering a prison, where he helped the prisoners to redecorate in order to make their surroundings more bearable. While the BBC deemed this subject a bit risqué for a children’s show, for McKee it is representative of the enduring theme of the series.

“Mr Benn was this idea that we all have things we’d like to escape from,” he says. “The prisoner is a little bit of a development of the same idea, in that all of us live in some kind of prison. It may be a very agreeable prison, and the idea was about making the best of the situation that we’ve actually got. That was not so different from the overall idea of Mr Benn.”

For the exhibition at the Illustration Cupboard in London, curator John Huddy has gathered together original drawings and paintings from the Mr Benn stories, as well as some acetates from the animations. The works fill the small gallery space though in fact there is surprisingly little archival material available from Mr Benn.

“At the time I gave some of the stuff away to people who were either close or working on the films and then most of the artwork I threw in a skip,” says McKee, somewhat devastatingly. “I didn’t have the storage, and I thought the finished product would be the film, and the artwork would not be needed. Of course what I didn’t think about is that someday it might have a value. So I probably threw away quite a bit of money there.”

There has been talk over the years of turning Mr Benn into a feature film, yet so far this has not come to pass. Fans will be cheered to hear though that, according to McKee, a plan for an upcoming film is chugging through development, which he approves of despite not being involved in its making.

“They’ve got a good script, it’s a case of if it goes past that very last stage of the company saying ‘yes, we will do it’. It’d be fun – I’d love to see him do that and say ‘oh, that’s what he’s up to, that boy of mine’.”

Mr Benn is of course not McKee’s only success. He’s the creator of a plethora of much-loved children’s characters, from Elmer the elephant, to King Rollo to a particular favourite of mine, Melric the magician. He describes them all in parental terms. “They’re all your children,” he says. “It’s quite interesting with Mr Benn now after 50 years … he’s got a right to live his life now without Daddy saying ‘oh, you can’t do that’.

“I think the air’s just full of stories,” he says of his inspiration for the characters. “In the way that it’s full of all those television programmes and all those radio programmes and all the telephone calls. If you’ve got the right apparatus you can pick them up. I think it’s full of music and it’s full of stories, and if you’re that kind of person, you tune in and pick one up.”

50 Years of Mr Benn is on show at the Illustration Cupboard in London until September 16; illustrationcupboard.com