Gangsta Granny at the Kings Theatre, Southsea

Decades later, when the adult David was a successful author, he decided to return to those days of his childhood and recreate that special bond between children and their grandmothers.

His best-selling novel Gangsta Granny was the result. Published in 2011, it went straight to number one in the children’s book charts and has been adapted for the stage by Birmingham Stage Company. It will play at the Kings Theatre, Southsea from January 19-23.

Ben has to spend every Friday night with his gran while his parents go ballroom dancing – and it’s always an ordeal of cabbage soup and Scrabble.

Then one day he finds a tin filled with diamonds and gems which leads to the amazing discovery that his granny was once an international jewel thief.

Persuaded by Ben, they decide to take on the biggest heist ever to steal the Crown Jewels and the adventure of their lifetimes is about to begin.

While David’s grannies were no mobsters, he admits that he did take a touch of inspiration from them.

‘When I was a child I would spend lots of time with my grandmas,’ he says. ‘Sometimes I would selfishly think spending time with them could be boring, but when I got them on a subject like living in London during the Second World War when bombs were raining down, they would become very animated and I would be enthralled. I realised everyone has a story to tell.’

David even added cheeky elements of their characters to his Gangsta Granny.

‘There was definitely a smell of cabbages in one of my grandmas’ houses,’ David admits. ‘The other did break wind like a duck quacking when she walked across the room.’

But they were also greatly loved – just as there is a special bond between Ben and his gran.

‘I think grandparents love being grandparents because they get to give the children back to the parents,’ says David. ‘Children love spending time with their grandparents because they love hearing their stories and being allowed to stay up past their bedtime.’

Writing for children is a real passion for him.

‘You can take children on magical journeys in books that many adults would be reluctant to go on,’ he says. 

‘Children love to be scared but it can’t be too horrifying.

‘Children love to laugh but it can’t be too rude. You always have to be the right side of the line.’

David has frequently been compared to Roald Dahl, his own childhood writing hero.

‘My favourite is The Twits which is utterly hilarious and I love that it is a children’s book with no child characters.’

David is hoping BSC’s Gangsta Granny will be the perfect outing for families.

‘The moral of the story is “don’t assume old people are boring just because they are old”’ he says.

‘In fact they are likely to have had a much more interesting life than yours. Talk to old folk, listen to their stories. They are bound to be full of magic and wonder.’

For tickets, visit kingsportsmouth.co.uk.