Sir Keir Starmer’s firebombed £2million house was reportedly being rented to his sister-in-law for a peppercorn amount as MailOnline can today reveal a 4x4 torched outside on VE Day was once owned by the Prime Minister.

A 21-year-old suspect has been arrested by Scotland Yard's counter-terrorism unit on suspicion of arson with intent to endanger life in relation to three blazes linked to the PM. He remains in custody.

Sir Keir's four-bedroom family townhouse in Camden had its front door doused in an accelerant and was sent alight in the early hours of Monday morning.

It is being reported that since entering No 10 Downing Street last summer, Sir Keir's sister-in-law has been living there. It is not known if she was at home at the time. The Prime Minister's official spokesman declined to comment today.

The alleged arsonist was held in South London this morning after the doors of two homes linked to the Prime Minister in north London both suffered fire damage within 24 hours of each other, one in the early hours of yesterday and another in the early hours of Sunday.