MI5 chief ​Ken McCallum apologised last year after the agency provided untrue information about a right-wing extremist who was a covert human intelligence source, sometimes referred to as an agent.

A BBC ​investigation found the MI5 agent, referred to in court as “Agent X”, ​had abused two former partners and told one of them, known only as “Beth”, that ‌he ⁠worked for MI5 in order to terrorise her.