However, of Agatha Christie herself, I knew precious little. That has now been filled in by Lucy Worsley’s fascinating biography, which I chanced upon recently. It is rightly subtitled A Very Elusive Woman. But once you have read it, you feel you know the author intimately.

Born to an American father, Christie was the surname she got from her first husband. Her only child, Rosalind, was from this marriage. It lasted from 1914 till 1928, when Archibald Christie’s infidelity led to a painful divorce.

Two years later Agatha married an archaeologist over a decade younger. It was on his digs in the Middle East that she got to know Iraq (Mesopotamia) and Egypt. Worsley reveals she financed much of her husband’s work. In return, she wrote Death on the Nile, Murder in Mesopotamia, and Murder on the Orient Express.

She was a devoted if somewhat jealous wife. A portable toilet was built for her so she could accompany her husband, Max Mallowan, to his archaeological sites. Worsley says it was, in fact, “a tea chest with a brass-hinged mahogany seat”.

Most of you probably know Agatha as an author of thrillers. But there was a lot more to her. Writing as Mary Westmacott, she authored six romantic novels. She was also an accomplished playwright. Two of her most famous plays are The Mousetrap and Witness for the Prosecution. The former ran continuously in a London West End theatre from 1952 till 2020, when it had to be temporarily discontinued because of Covid. It reopened in 2021.

Poirot is by far her most famous creation but, in fact, she thought he was “rather insufferable”. Following his last appearance in Curtain in 1975, the New York Times published his obituary on its front page.

Agatha lived to be 86 and Worsley reveals she was writing well into her 80s. When she died “her last notebooks still contain ideas for yet another novel. It was to feature an entirely new idea, about two students who murder a boy purely as an experiment.”

Not surprisingly, mystery surrounded Agatha’s own life. In 1926, when her marriage with Christie was teetering, she disappeared for ten days. A massive manhunt was conducted but no one knew where she was. Worsley says her critics considered her “a manipulative minx”, determined to seek revenge on her adulterous husband. But it seems she was going through a mental breakdown. Worsley inclines to that view.

However, the joy of Worsley’s book is not just the broad sweep of the story she tells but also the small little nuggets she reveals. They surprise, like little gifts on a treasure hunt.

Agatha’s great career stumbled at its very start. Her first book, The Mysterious Affair at Styles, was rejected by two publishers before The Bodley Head took it on. At 36, she weighed 11 stone. That went up to 13 in later years. She was certainly a big woman. And Agatha loved houses. She owned eight!

But she could be quite careless. Worsley points out that Poirot lives in Whitehaven Mansions except when he lives at Whitehouse Mansions. In Sleeping Murder, a clerk, a receptionist and a train passenger are all accidentally given the same name, Narracott, which is also the name of a chambermaid, a boatman and a policeman in three completely different books.

After a heart attack in 1974, Agatha was asked how she’d like to be remembered. “A rather good writer of detective stories,” was her reply. I would never disagree.

Karan Thapar is the author of Devil’s Advocate: The Untold Story. The views expressed are personal