It is 120 years since the queen of crime writers Agatha Christie was born and search engine Google is celebrating with a doodle on its home page depicting her fictional detective Hercule Poirot

Google has marked the 120th anniversary of the birth of the queen of crime fiction Agatha Christie this morning with a doodle on its home page. The search engine's letter G has been transformed into the author's moustachioed detective, Hercule Poirot.

Christie is not the first author Google has honoured – the search engine has also created sketches on its home page for HG Wells and The Little Prince author Antoine de Saint-Exupéry – but she is undoubtedly the most prolific and bestselling. Born on 15 September 1890, the crime novelist is, with sales of over 2bn books worldwide, outsold only by Shakespeare and the Bible, her publisher, HarperCollins, says. Christie's 80 novels and short story collections have never been out of print since her death in 1976 – when all of London's West End theatres dimmed their lights for an hour to mark her passing – and still sell a million copies a year, according to HarperCollins.

The Google doodle shows Poirot – the only fictional character ever to receive a full-page obituary in the New York Times – and a cast of characters standing around a body (the search engine's letter "o", in this case wearing a set of pearls), as the Belgian detective undoubtedly explains exactly whodunit to his less perceptive observers.

Christie never set out to be a writer, but she rose to the challenge when her sister Madge dared her to write a detective story. Her path to publication wasn't easy: six publishers initially rejected The Mysterious Affair At Styles, and it took five years for the Bodley Head to get in touch and offer her a deal – for £25.

She moved to Collins for perhaps her most famous book, The Murder of Roger Ackroyd, in 1926, and stayed with the publisher from then on, publishing a "Christie for Christmas" every autumn from 1936 until her death 40 years later.

In 1976, William Collins recalled meeting Christie as a young author shortly after publication of the genre-twisting novel had made her famous, over 50 years earlier. "The blurb of her new detective novel gave away a vital clue, and my uncle sent me, young and innocent, to break the terrible news," he said. "I was received with the greatest kindness, but little did I think that this was the beginning of a long and very special personal friendship with one of the most wonderful and modest people I have ever met."

As well as the Google doodle, Christie's 120th anniversary is also being commemorated with Jane Asher's creation of a chocolate cake inspired by the Miss Marple tale, A Murder is Announced, and with "Christie Week" celebrations around Britain. HarperCollins, meanwhile, is marking the occasion with a new book deal to become the author's exclusive worldwide English language publisher, with plans to push her sales to "even greater heights" around the world.