Did Holmes's creator hide the elementary answer on Piltdown Man?

In a deduction worthy of Sherlock Holmes, a science historian yesterday publicly implicated Sir Arthur Conan Doyle in the infamous Piltdown Man hoax, citing the renowned author's own silence on the celebrated palaeontological prank to back his case.

Richard Milner, a historian at the American Museum of Natural History in New York, said that although the 1912 "discovery" of remains of the so-called "Earliest Englishman" took place close to Sir Arthur's home, near to where he played golf and that he knew the characters involved, there had been no overt reference to the matter in any of his writings.

Referring to the author's fictional detective, Mr Milner said: "It is like the dog that did not bark in the night. Why didn't Sir Arthur refer to it? It was a very exciting find."

The riddle of who carried out the bone hoax - exposed in 1953 as a mixture of a human skull and orang-utan jaw - has long intrigued scientists and historians. Early suspects included Charles Dawson, the solicitor who found the remains in a Sussex quarry, later widening to Sir Arthur as well. Last year, Professor Brian Gardiner, of King's College, London, said he was "100 per cent" certain that the hoaxer was Martin Hinton, the Natural History Museum's curator of zoology in 1912.

Yesterday, in a debate organised by the Linnean Society, (named after the inventor of the system of Latin classification for flora and fauna), Mr Milner, Professor Gardiner and other experts put forward rival theories for the culprit.

Mr Milner said that his main evidence against Sir Arthur was his motive, and clues in his novel The Lost World - in which a scientist announces the discovery of dinosaurs to a sceptical scientific establishment.

He rejects the theory that the hoax was perpetrated by a scientist trying to make a reputation, and suggests the instigator was someone trying to show up the gullibility of scientists.

The writer's motive, said Mr Milner, came from his devotion to spiritualism, a belief widely ridiculed by scientists.

In particular, Sir Arthur was angered by the prosecution of his favourite psychic, Henry Slade, by an evolutionist in 1876.

"Conan Doyle had the deepest kind of motive for wanting to take revenge on scientists," said Mr Milner. The author had exploited English scientists' desire to find their own prehistoric human bones at a time when both France and Germany already had their own collections.

Mr Milner also believes Sir Arthur left an abundance of clues in The Lost World - published in the same year as the hoax - that suggest he was behind the staining and placing of the bones. One of its characters is quoted saying that faking bones was as easy as faking photographs. The book also contains a key, containing 18 characters, which Mr Milner believes is a cryptogram holding the solution to the Piltdown hoax, a device he may have borrowed from Jules Verne.

"I think Conan Doyle wanted to be discovered quite quickly," said Mr Milner. However, as the outbreak of war loomed, Sir Arthur had wanted to advise the Government on the dangers of German U-boats, and thus did not want to be known as a hoaxer.

"The cryptogram changed from edition to edition - I think he thought that as the secret was not discovered quickly he would obscure it."

Mr Milner said he was confident of his theory, but conceded that the riddle was unlikely to be solved definitively unless some "genius" cracked the cryptogram, or unless private papers of Sir Arthur, which may be available for study in the next few years, revealed his involvement.

"I am not trying to denigrate Conan Doyle, he was a very honourable man. I think no less of him for doing it - he believed it was the most important thing in the world to convert people to what was essentially his religion," said Mr Milner.

Celebrated hoaxes of the 20th century

The famous 1934 picture of the Loch Ness monster in fact showed a model based on a Woolworth's toy submarine with a plastic head made by a team of hoaxers.

In 1938, six million listeners to CBS radio heard a "news bulletin" announcing an invasion by Martians. People took to the streets in panic, thinking the broadcast, which was part of Orson Welles's adaptation of War of the Worlds, was really taking place.

The German forger Konrad Kajau fooled eminent historians and The Sunday Times with Hitler's diaries, which he wrote to pay for a drunken affair.

In 1995, the Queen was tricked into broadcasting a message of support to Canada by a DJ called Pierre Brassard posing as the Canadian Prime Minister, Jean Chretien.

A Capital Radio DJ once announced that because of the adjustment between GMT and BST, 5 April and 12 April had been cancelled.