Known by a number of other aliases, he racked up a string of convictions, but none for terrorism-related offences. His occupation was unclear.

It was as long ago as November 1983 that he first came to the attention of authorities when he was found guilty of causing criminal damage, while his last conviction came 14 years ago in December 2003 for possession of a knife.

Little detail has officially been given about the man and what might have led him to carry out Wednesday's attack, the deadliest in Britain since the London suicide bombings of 2005 by four young British Islamists, which killed 52.

"Our working assumption is that he was inspired by international terrorism," said Britain's most senior counterterrorism police officer, Mark Rowley, adding: "Islamist-related terrorism is our assumption."

One of his former neighbours in Birmingham said: "When I saw the pictures on TV and in the papers of the man who carried out the attack, I recognised him as the man who used to live next door."

The Daily Mail newspaper said Masood had been born Adrian Elms and was brought up by his single mother in the seaside town of Rye on England's south coast, later converting to Islam and changing his name.

Other media reports said he was a married father of three and a former English teacher who was into bodybuilding.

Birmingham has been one of the hotbeds for British Islamists. According to a study by the Henry Jackson think tank earlier this month, 39 of 269 people convicted in Britain of terrorism offences from 1998 to 2015 came from the city.

There are over 213,000 Muslims in Birmingham, making up over a fifth of the population, according to the 2011 census, and there has been growing concern about divisions in the diverse city.

Reuters