Counter terrorism police are mystified over the motive for the firebomb attacks targeting Sir Keir Starmer.

Officers are set to ask for more time this afternoon to question a 21-year-old alleged arsonist arrested on suspicion of targeting the Prime Minister’s £2million family home in Kentish Town after torching a car and another property he had previously owned.

Specialist detectives from Scotland Yard's SO15 counter-terror branch are exploring various lines of inquiry which will include whether a fixated individual bore a personal grudge against Sir Keir.

Today there were claims that a hostile state may be responsible for the three arson attacks between May 8-12.

In the last year, MI5 investigations into hostile state threats have risen by almost 50 per cent following a surge in assassination, kidnap, arson and sabotage plots.