Britain on Tuesday (September 22nd) handed to US authorities evidence related to two members of an "Islamic State of Iraq and Syria" (ISIS) murder cell dubbed the "Beatles", clearing the way to a trial after Washington said it would not seek the death penalty.

The evidence regarding El Shafee Elsheikh and Alexanda Kotey "has now finally been transferred to the US", British Home Secretary Priti Patel said on Twitter.

"I sincerely hope that justice for the victims and their families will now be served," she said.

The transfer of material intended to help the prosecution of the pair -- who have been stripped of UK citizenship -- came after Elsheikh's mother lost a legal challenge in the London High Court.

Maha Elgizouli's lawyers had told the court that Patel's decision to press on with the transfer breached Britain's Data Protection Act.

But the judges ruled that the home secretary was within her rights.

"The conclusion that, even if Mr Elsheikh could be prosecuted in England, it would still be necessary and proportionate to transfer the data to the US authorities remained a conclusion properly open to the secretary of state," the ruling said.

A two-year legal impasse concerning the pair -- who are in the custody of US forces in Iraq -- was broken last month when Attorney General Bill Barr said they would be spared execution if convicted after trial in the US.

But he warned that unless the British evidence was shared by October 15th, Kotey and Elsheikh would be handed over for prosecution and possible execution in Iraq.

Barr's intervention put the onus on Patel to see if the British system could overcome the court challenge by Elsheikh's mother and share the evidence, said to be damning wiretaps, with US authorities.

The US wants to try the two for the murder of journalists James Foley and Steven Sotloff, and aid worker Peter Kassig, during a period in 2014-2015.

Kotey and Elsheikh's four-member cell was dubbed "the Beatles" by their captives due to their British accents. They tortured and killed victims, including by beheading, and ISIS released videos of the deaths for propaganda purposes.