10 things you didn't know about Agatha Christie

1: Move over, Rowling

Forget Harry Potter. Agatha Christie is, even by conservative estimates, the bestselling fiction writer of all time.

At least a billion copies of her novels have been sold in English alone, with a further billion sold in over 100 other languages. On top of this, her stageplay The Mousetrap is the longest running play in the world, beginning in 1952 and still going strong today.

2: Christie the crooner

Agatha originally wanted to be a singer rather than a writer, showing great talent at school.

Despite her singing prowess, stage fright often got the better of her and her tutor predicted she would never muster the courage to become a professional singer. The yearning never left her though, and she still spoke wistfully of wanting to be an opera singer when she was in her 60s.

3: Hands-on research

Agatha Christie's first novel was inspired by her stint as a nurse during World War One.

She worked at a Red Cross hospital set up to treat wounded soldiers transported back from the war on the Continent. She was eventually promoted to the dispensary where she was responsible for mixing drugs and handling toxins – and her resulting knowledge of poisons led her to write her debut book The Mysterious Affair at Styles.

4: A very British writer (sort of)

Agatha may have seemed the very image of the stately English lady (the "Queen Mother with a pen", as one journalist called her), but she was in fact half-American.

Her father, Frederic Miller, was a rich American stockbroker who had moved to Britain many years before Agatha was born. Her mother, Clara Boehmer, was an aristocrat, which might explain why so many of Agatha's novels deal with wealthy, well-to-do types.

5: A true life mystery

Agatha herself became the centre of a mystery when she went missing for 11 days in 1926.

A national furore ensued when the writer disappeared – her car was found abandoned, and many believed she'd been murdered or had committed suicide. Even Sherlock Holmes creator Arthur Conan Doyle became engrossed, taking one of Agatha's gloves to a medium in the hope of tracking his fellow crime writer down. Ultimately, Agatha turned up alive and well at a hotel in Harrogate, where she had checked in under the name of the woman her husband had been having an affair with. The question of why exactly she ran away is still argued over today.

6: Killing the golden goose

Agatha killed off Poirot in the 1940s (around 20 years after creating him with her first novel, The Mysterious Affair at Styles) because she was worried she'd die before giving him a suitably dramatic finale.

Concerned about the German bombing raids during World War Two, Agatha wrote a book called Curtain – in which Poirot succumbs to a heart condition. She had the book stored in a bank vault and continued to write Poirot novels for years afterwards. It was only in 1975, when she realised she had no more books in her, that she authorised the publication of Curtain. It was a worldwide sensation, and – despite being a fictitious character – the detective was even awarded a front page obituary in the New York Times.

7: Agatha's alter-ego

Agatha Christie didn't just write crime stories. She also published several romances under the name Mary Westmacott.

With titles like Absent in the Spring and Unfinished Portrait, they are rich melodramatic yarns featuring tortured artists, rekindled romances and sudden bursts of tragedy. Being so brazenly emotional, they're a far cry from her meticulously controlled crime novels.

8: The other detectives

Poirot and Miss Marple were far from the only detectives Agatha came up with.

Take Tommy and Tuppence, for example. She wrote several books about this sassy couple who delight in solving mysteries and embarking on adventures. Unusually, the characters actually age in "real time" during the course of the books, and end up as proud grandparents in the last one. Another of Christie's creations is Parker Pyne, a quirky detective who specialises in "bringing happiness" to his clients (and even helps improve their love lives).

9: The original Marple

Miss Marple was actually inspired by a character Agatha developed for a Poirot story called The Murder of Roger Ackroyd.

The character in question is a mature but wily spinster named Caroline Sheppard. Explaining why she used Sheppard as the template for Marple, Agatha later said: "She had been my favourite character in the book – a spinster full of curiosity, knowing everything, hearing everything." Incidentally, the village of St Mary Mead, which features so heavily in the Marple tales, was first created for a Poirot story called The Mystery of the Blue Train.

10: Indiana Agatha

Agatha was a keen amateur archaeologist and travelled the world in search of relics to clean and preserve.

Thanks to her marriage to the celebrated archaeologist Max Mallowan, Agatha was able to access some of the most remarkable (and toughest) digs in the world. She had a particular interest in Iraq, where she spent a long period working and sleeping in a tent. She photographed and catalogued many great artefacts, using her own rather expensive face cream to polish and restore the ancient objects.