“He said he lived above a guitar shop in Birmingham but he’s not originally from the Midlands and had a London accent. But he said London wasn’t like what it used to be. Police told us later it was definitely the Westminster attacker.”

According to The Sun, Masood stayed at the hotel on Friday night, checked out the following morning, then checked back in on Tuesday for one more night.

"Everyone says he was nice and polite and acted totally normal," the source was quoted as saying.

Police are investigating where Masood visited between his stays at the hotel. On Monday or Tuesday, he turned up at the car hire company Enterprise at its Spring Hill depot in Birmingham and rented the Hyundai SUV used in the attack.

Masood's “violent extremism” had caused security services sufficient alarm to put him under investigation as long as a decade ago.

But by the time he carried out the attack on Wednesday, the father of three was no longer considered a threat. Police have detailed his long history of violent crime. But none, they stressed, was for terrorism offences.