An undercover agent who foiled an al-Qaeda plot to blow up a airliner with an underwear bomb is a British national, according to US reports.
UK intelligence were said to have been "heavily involved" in recruiting the spy who infiltrated a terror group in Yemen in a rare coup for western agencies.
Quoting sources briefed by Saudi counter-terrorism officials, US television networks said the individual grew up in Europe where he was apparently radicalised.
He was subsequently "turned" and recruited by Saudi agents last year, they said.
The reports were neither being confirmed nor denied in the UK.
The device is similar to a bomb sewn into the underwear of a man who tried and failed to set it off over Detroit on Christmas Day 2009.
Al-Qaeda in the Arabian Peninsula is believed to have been planning the spectacular attack, with a nearly-undetectable device, around the anniversary of the death of Osama bin Laden.
But the individual chosen to carry out the attack was an informant who handed over the bomb.