Dennis Yates (or Yeats) Wheatley was born in South London to Albert David and Florence Elizabeth Harriet Wheatley (née Baker). He was the eldest of three children of an upper middle class family, the owners of Wheatley & Son of Mayfair, a wine business. He was expelled from Dulwich College. The school had already been attended by two prominent writers: P.G. Wodehouse (1894-1900), and Raymond Chandler (1900 onwards). Following his expulsion Wheatley became a Merchant Navy officer cadet at the training ship HMS Worcester.
He took part in the First World War but was gassed in a chlorine attack at Passchendaele and invalided out as a second lieutenant in the Royal Field Artillery after seeing service in Flanders, on the Ypres Salient, and in France at Cambrai and St. Quentin. He took over the family wine merchant business in 1919, but following a decline in business after the depression in 1931, he set about writing and married his second wife.
During the Second World War, Wheatley's literary talents led him onto planning staffs for the War Office. He wrote numerous papers for the War Office, including drawing up suggestions for dealing with a German invasion of Britain (recounted in his work "Stranger than Fiction"). The most famous of his submissions to the Joint Planning Staff of the war cabinet was on "Total War". He was given a commission directly into the JPS as Wing Commander, RAFVR and took part in advanced planning for the Normandy invasions.
His first book, Three Inquisitive People, was not immediately published; but his first published novel, The Forbidden Territory, was an immediate success when published in 1933, being reprinted seven times in seven weeks.
He wrote adventure stories, with many books in a series of linked works. His plots covered the French Revolution (Roger Brook Series), Satanism (Duc de Richleau), World War II (Gregory Sallust) and espionage (Julian Day).
In the thirties, he conceived a series of whodunit mysteries, presented as case files, with testimonies, letters, pieces of evidence such as hairs or pills. The reader had to go through the evidence to solve the mystery before unsealing the last pages of the file, which gave the answer. Four of these 'Crime Dossiers' were published: Murder Off Miami, Who Killed Robert Prentice, The Malinsay Massacre and Herewith The Clues.
In the 1960s his publishers were selling a million copies of his books per year. A small number of his books were made into films by Hammer, of which the best known is The Devil Rides Out (book 1934, film 1968). His writing is very descriptive and in many works he manages to introduce his characters into real events while meeting real people. For example, in the Roger Brook series the main character involves himself with Napoleon, and Joséphine whilst being a spy for the Prime Minister William Pitt. Similarly, in the Gregory Sallust series, Sallust shares an evening meal with Hermann Göring.
He also wrote non-fiction works, including accounts of the Russian Revolution and King Charles II, and his autobiography. He was considered an authority on the supernatural, satanism, the practice of exorcism, and black magic, to all of which he was hostile.
From 1974 though 1977 he edited a series of 45 paperback reprints for the British publisher Sphere under the heading "The Dennis Wheatley Library of the Occult," selecting the titles and writing short introductions for each book. This series included both occult-themed novels by the likes of Bram Stoker and Aleister Crowley and non-fiction works on magic, occultism, and divination by authors such as the Theosophist H. P. Blavatsky, the historian Maurice Magre, the magician Isaac Bonewits, and the palm-reader Cheiro. Two weeks before his death in November 1977, Wheatley received conditional absolution from his old friend Cyril ‘Bobby’ Eastaugh, the Bishop of Peterborough.
His estate library was sold in a catalogue sale by Basil Blackwell's in the 1970s, indicating a thoroughly well-read individual with wide-ranging interests particularly in historical fiction and Europe. His influence has declined, partly due to difficulties in reprinting his works owing to copyright problems. Fifty-two of Wheatley's novels were published posthumously in a set by Heron Books UK. More recently, in April 2008 Dennis Wheatley's literary estate was acquired by media company Chorion.
His work is fairly typical of his class and era; it contains a quality of life/clubland snobbery that gives a good insight into the values of the time, good and bad. His leading characters are all dyed-in-the-wool supporters of Royalty, Empire and the class system and many of his villains are villainous because they attack these ideas, although in a work such as The Golden Spaniard he has various protagonists pitted against each other set in the Spanish Civil War. His works are enjoyable thrillers, and his "Roger Brook" series in particular offer the reader "history without tears" (Wheatley, in the introduction to The Man Who Killed the King). His historical analysis is coloured by his politics, but is well informed. For example, the books set in Spain have a discussion of anarchism which is well grounded, though unsympathetic. His strong attachment to personal liberty also informs much of his work. This, as well as a sympathetic attude toward Jews (as shown in the 'Simon Aron' character introduced in 'Three Inquisitive People') led him to mercilessly flay the Nazi system in those 'Gregory Sallust' thrillers set in World War Two.
In the winter of 1947 Wheatley penned 'A Letter to Posterity' which he buried in an urn at his stately home. The letter was intended to be discovered some time in the future. In it he accurately predicted that the socialist reforms introduced by the post-war government would inevitably lead to an unjust state, and called for both passive and active resistance to it.