Two Londoners suspected of being part of an Islamic State execution cell dubbed “the Beatles” should face justice by “locking them up and throwing away the key”, a police chief has said.

Opinions are divided on the fate of Alexanda Kotey and El Shafee Elsheikh, who were captured in Syria in January and are accused of links to a string of hostage murders in Iraq and Syria.

Last week, Home Secretary Amber Rudd left the door open for the pair to face trial in the UK, after Defence Secretary Gavin Williamson said they should not return to Britain because they had “turned their back on British ideas, British values”.

The US wants other countries to take responsibility for their own citizens arrested in the fight against IS.

Asked about the fate of the pair on Monday, Met Assistant Commissioner Mark Rowley, who leads the UK’s counter-terrorism policing, said: “The people who have done the most ghastly things overseas, the ones who don’t fight to the death, we would all like to see them never able to do anyone any harm ever again. Locking them up and throwing away the key would be a great idea.”

Mr Rowley spoke to journalists ahead of a speech on Monday, expected to be one of his final public engagements before he retires from policing next month.

Jihadi John killed
British extremist Mohammed Emwazi, known as Jihadi John, was killed in 2015 (PA)

Along with Mohammed Emwazi – the killer nicknamed Jihadi John – and Aine Davis, Kotey and Elsheikh are thought to have been part of a group named after the 60s band because of their English accents.

Emwazi, who was killed in a US air strike in 2015, appeared in a number of videos in which captives including British aid workers David Haines and Alan Henning were beheaded.

Davis was convicted of being a member of a terrorist organisation and jailed for seven-and-a-half years at a court in Silivri, Turkey, in May 2017.