The last book about the crime-fighting children was written in 1963 and now producers want to show them grown up in a new drama that has been authorised by Blyton's estate.

Independent production company Twofour will develop the series, which will show the characters aged between 40 and 50. Having gone their separate ways, they are reunited to fight a new crime.

A source told The Times: "They would all be in middle age, perhaps some of them would be going through midlife crises.

"It will be interesting to see whether the characters have grown up to be like they were when they were children. Would George, the tomboyish one, now be glamorous and have lots of children? Would Anne, the sensible one, be dysfunctional?”