Spontaneous human combustion is a phenomenon as rare as it is puzzling. But such is the bafflement surrounding the death of a pensioner who caught fire in the street, some are now speculating that the gruesome scientific anomaly is to blame.

John Nolan, 70, died from “horrific” burns after being found ablaze near his home in North London in September. Detectives have now said that after weeks of investigation they have found no obvious cause for the fire.

Spontaneous human combustion is a fiercely debated process, characterised by near-total destruction of the body with little surrounding damage.

It has been attributed to fewer than 200 deaths in history and was famously depicted in Dickens’ Bleak House where the alcoholic Krook combusts with no apparent cause.

Mr Nolan, described as a “gentle, nice man”, had no accelerants on his body, according to police, and Fire Service investigators found no source of ignition.

Yet relatives later said he suffered burns to his internal organs.

Originally from County Mayo, the former construction worker was airlifted to Colchester hospital and died surrounded by family members after doctors withdrew life-support.

PC Damien Ait-Amer, who is investigating the death, said: “Mr Nolan was a well-liked member of the community and none of our enquiries so far have indicated that he had been involved in a dispute of any sort, nor does any account given by witnesses suggest that he had been in contact with another person at the time of the fire.”