The story centres on an Egyptian-style mausoleum in Brompton Cemetery - and I finally got to visit it on a crisp autumn day in October, in the approach to Halloween.
Brompton Cemetery, in the London Borough of Kensington and Chelsea, was established in 1836 and opened in 1840 as one of Victorian London's much-needed new burial grounds at the time. It is run by the Royal Parks and is unusual in that it is the only Crown Cemetery.
Another unusual thing about Brompton is that, as graveyards go, it has very few ghosts. London's other cemeteries - such as Highgate, Nunhead and Kensal Green - are most decidedly haunted, but the dead at Brompton seem to genuinely rest in peace.
That is, unless tales of time travel are to be believed - first revealed to the public in newspaper headlines in the last decade of the 20th century.
A Reuters story dated October 10, 1998 stated:
"Shrouded by trees in the middle of London's Brompton cemetery stands a strange, imposing structure carved with elaborate Egyptian-like figures that has been exciting the interest of writers and researchers. The 150-year-old mausoleum is the only one in the cemetery for which no plans can be found.
"Its occupants are a mysterious trio of spinsters about whom almost nothing is known. Intrigued by the tomb, writer Howard Webster began researching its origins and now believes the 20-foot tall building was a time machine built by a maverick Victorian genius, Samuel Warner, who also invented the torpedo. Warner is buried in an unmarked grave about 70 feet from his creation and in another nearby grave lies his likely collaborator, architect and Egyptologist Joseph Bonomi."
What adds to the mystery is that some people believe Warner, who was in negotiations over his plans for aerial bombs and sea mines with Duke of Wellington, commander in chief of Britain's army, was either murdered to prevent his designs for weapons falling into the wrong hands, or by someone who stole them from his dead body. However, others believe Warner was either a crackpot or a fraud whose inventions could never have worked.
Warner's colleague Bonomi was in the team of Egyptologists and archaeologists who first deciphered the hieroglyphic texts found on papyri in Egypt's Valley of the Kings.
James Mackay, a spokesman at Brompton cemetery, reportedly said at the time of the Reuters story: "It could be that some of the papyri they were decoding dealt with time travel."
The Victorians were fascinated with theories about time travel - exemplified by HG Wells' book The Time Machine. They also came up with the idea that the ancient Egyptians might have had devices that could transport people through time and space - a concept used in the film and TV series Stargate.
Webster speculated that if Warner and Bonomi had come up with plans for a time machine, they would have needed considerable funds to build it. Their backer could have been the three women who supposedly occupy the tomb - Hannah Courtoy and her two daughters Mary Anne and Elizabeth.
Courtoy was not Hannah's real name, but one she used for convenience because she was the mistress of wealthy merchant John Courtoy. She outlived him and some speculate that she later became the mistress of royalty. She knew Bonomi and may have funded his expeditions.
The Reuters story went on to explain why Hannah's tomb was thought to be a time machine:
"The trapezoid of dark polished granite is decorated with narrow bands of carved hieroglyphics and has a huge bronze door for which there is no surviving key. It has not been opened for more than 120 years. Sixty feet away, Bonomi's gravestone bears similar hieroglyphic carvings including the Egyptian god of the dead, Anubis, sitting on what appears to be a replica of the mausoleum. Webster believes this is a vital clue to the mausoleum's secret. The direction Anubis is facing - toward the mausoleum - suggests in Egyptian mythology a soul lost out of time."
In 1998, Mackay said he thought that Warner was a hoaxer who might have conned the Courtoys into believing he could build a time machine. However, he added: "The biggest mystery is that you couldn't build anything in the cemetery without plans and there are no plans. His choice of the cemetery was a shrewd and appropriate one ... it was one of the few places where one could work unobserved and where even the most eccentric of structures could be explained away. A cemetery where the wealthy and famous are buried is also a location that one could say with great certainty is unlikely to be the subject of redevelopment over time ... like Egyptian tombs, where structures could remain intact over centuries.''
Hannah Courtoy died in 1848, but her mausoleum was not finished until 1853 - the same year Warner died and when Bonomi's headstone stone was erected. Webster said: "I like to believe that Warner's is not the body in the unmarked grave but that he is still alive and travelling through time in his machine.''
The story of the Brompton Cemetery Time Machine grew in fame in 2003, when the Courtoy mausoleum was used as the cover picture for the ambient electronic album Musick That Destroys Itself by Mount Vernon Astral Temple.
It contains two tracks: Warner's Reverie and London Praises Its Ancient God, which reviews describe as "spacey".
Yet the album's title could almost be considered a premonition, because not long after it was released, the mausoleum began to self-destruct. Chunks of granite began to fall from its surface and cracks appeared in the lintels above the doors.
Someone I spoke to in the cemetery, who did not give their name, said: "It could be entropy catching up with it or might have been struck by lightning while journeying through time. Who knows what could happen if it malfunctioned?"
"I wouldn't stand too close," they added.
Arthur Tait of the Friends of Brompton Cemetery gave a far more rational explanation for the damage. "It was caused by frost two or three winters ago," he told me.
He said: "It will cost several thousand pounds to have it restored. Unfortunately, the Royal Parks do not have the necessary money available. We have told them that the Friends would be willing to contribute a bit towards the cost, however no action yet. I hope we can get progress on this next year."
At the moment, the mausoleum is in a sorry state, with lumps of fallen rock lying at its base, its steps overgrown with weeds and its main metal doorway tarnished and discoloured. It is surrounded by a wire fence with signs warning people to "Keep out".
Time machine or not, it would be a shame if the mausoleum is left to crumble. Perhaps some mysterious benefactor, strangely attired in outlandish clothing, will turn up one day soon to donate the necessary money to restore it to its former glory? I do hope so...
Musick That Destroys Itself
The Time Machine (Penguin Classics)
Stargate S.G. 1 - Series 1-10 - Complete/The Ark Of Truth/Continuum [DVD]