When I first heard the news that the BBC was producing a new Hercule Poirot prequel – featuring heartthrob Edward Bluemel as a young, sexy version of the detective – I had my valet prepare me a cup of fortifying tisane. As a lifelong enthusiast for the works of Agatha Christie, the “Queen of Crime”, I am used to regular sacrileges. Yet the pace at which the estate is being gouged appears to be quickening, a story that tells us much about the rotten core of the modern entertainment complex.

It has been reported this week that Agatha Christie Limited, the company that operates the writer’s estate, made pre-tax profits of more than £20m last year. That has made her descendants extremely wealthy, some 50 years after Christie went the way of Roger Ackroyd, Lord Edgware and Mrs McGinty. When the author died in 1976, Robert Knittel, the editorial director of her publisher, reflected on her enormous impact. He observed that she “was read all over the world, including Russia, was translated into 28 languages and in her lifetime her thrillers had sold about 300 million copies”. In the half-century that has passed since then, that figure has risen to more than two billion. It is widely claimed that her sales record is surpassed only by William Shakespeare and the Bible.