Even the great fictional traveller Phileas Fogg would have baulked at such a wager: walk around the world while pushing a pram and wearing an iron mask, and pick up a wife along the way without ever letting her see your face or know your name.

Just to make it a little more interesting, you can set off with only one change of underwear and £1 in your pocket and your sole source of income must be the sale of postcards.

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Harry Bensley became a celebrity after trekking 30,000 miles across 19 countries

Harry Bensley accepted the wager with John Pierrepoint Morgan, the founder of JP Morgan Bank, and Lord Lonsdale, in 1908, for £21,000 - equivalent to £1.5 million today.

He became an Edwardian celebrity after trekking 30,000 miles across 19 countries over six years. As compensation, he was given £4,000.

However, on the 100th anniversary of his departure from Trafalgar Square his great-grandson fears that his ancestor may have told a fib or two.

Despite more than 20 years of research he has not found a shred of evidence his ancestor ever left Britain.

"It seems very odd that he leaves in a blaze of publicity and then there is nothing about him until he re-emerges six years later claiming to have travelled around the world," said Ken McNaught, 49, of Wakefield, Yorks.

"I suspect that he disappeared for five years, probably to France, and came back at the outbreak of the First World War."

His ancestors now believe the journey was more likely a forfeit after Bensley, a well known chancer and playboy, lost his fortune in a game of cards with the two men.