A British-born man who was a member of a team of militants of the so-called Islamic State in Syria nicknamed 'The Beatles' has pleaded guilty to eight US criminal charges including lethal hostage taking and conspiracy to support terrorists.
London-born Alexanda Kotey is one of two IS members who were held in Iraq by the US military before being flown to the United States to face trial on terrorism charges.
Appearing before US District Judge TS Ellis at a hearing in Alexandria, Virginia, Kotey pleaded guilty to the murders of US journalists James Foley and Steven Sotloff and aid workers Kayla Mueller and Peter Kassig.
The charges carried potential death sentences, but US authorities have advised British officials that prosecutors will not seek the death penalty against Kotey.
Judge Ellis said that under a tentative arrangement between US and British authorities, Kotey could be transferred to Britain after 15 years' imprisonment.
The Justice Department said in a statement that given that Kotey agreed to life imprisonment without parole, if the sentence he serves in the UK is less than life for any reason, Kotey agreed "to be transferred back to the United States to serve the remainder of his sentence."
Judge Ellis added that as part of the plea, Kotey had agreed to "full complete and truthful" cooperation with US and foreign government investigators and to supervised meetings with members of the families of hostage victims.
Kotey was a citizen of the UK, but the British government withdrew his citizenship.
He belonged to a four-member Islamic State cell nicknamed "The Beatles" because of their British accents.
The cell was suspected of taking part in graphic Islamic State videos posted online showing beheadings of foreign hostages.
A 24-page indictment includes a lengthy list of acts of torture that Kotey is accused of inflicting on hostages, including electric shocks with a taser, forcing hostages to fight each other and beatings with sticks and waterboarding.
The mother of journalist James Foley has asked for answers after Kotey pleaded guilty to being involved in the murder of multiple hostages.
Diane Foley urged Kotey to give up information about the IS cell and said she hoped Kotey's cooperation with authorities would extend to telling the family members of the cell's captives where their loved ones' remains are, and whether anyone else was involved in the plot.
Mrs Foley said: "I didn't get any indication he's interested in (making amends) but I hope in time he might just because the extent of the evil he has committed is - I just don't know how any soul could live with all that.
"All of us would like to know where the remains of our children are."
Kotey and fellow "Beatle" El Shafee Elsheikh are also suspected of involvement in the killings of others, including humanitarian David Haines, from Perth in Scotland, and aid worker Alan Henning from Lancashire.
Elsheikh, who was captured alongside Kotey in 2018, is scheduled to stand trial next year, while fellow cell members - ringleader Mohammed Emwazi, known as Jihadi John, and Aine Davis - are dead and in jail respectively.
Mrs Foley, who was in court for Kotey's plea, said her son's killer looked at her "briefly" during the two-hour hearing.
She said: "It was rather chilling to be there, it's the first time we've ever seen him in person.
"The fact that he was pleading guilty to all eight counts was quite amazing really."
Additional reporting PA