David Whitelaw was born in Holloway in London. Both of his parents died during his infancy and he and his elder brother Stephen were raised by their grandparents, Theodore and Eliza Baxter, members of the North London branch of the Sandemanian church.
After brief spells in New York and Paris in the 1890s, Whitelaw returned to London to work for various Fleet Street newspapers as an illustrator and journalist, later becoming editor of The London Magazine and The Premier Magazine. The Premier Magazine, published by the Amalgamated Press, (based at Fleetway House in Farringdon, London) ran between 1914 and 1931 and published atmospheric adventure and mystery fiction including authors such as Edgar Wallace, Sax Rohmer, Rose Champion de Crespigny and Achmed Abdullah.
His first novel "M'Stodger's Affinity" was published in 1896 and this was followed by a steady output of romantic thrillers. He had over 50 novels published during his lifetime and his stories were also serialised in the Amalgamated Press published The Thriller magazine. Many of his works went through multiple publication runs and translation into numerous languages. He also wrote several plays for stage and television.
In 1936 he invented the spelling card game Lexicon, which won worldwide popularity. In his 1944 book "The Lexicon Murders" the killer uses the card game for the purpose of a secret code. Lexicon has been translated into many languages and Braille. It is still in production today.
He was for many years a member, and later chair of, The Savage Club.