An undercover agent who foiled an al Qaeda plot to blow up a airliner with an underwear bomb is a British national, it was reported tonight.
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.
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.
The details provided by the agent led to a CIA-directed drone attack in Yemen which killed Yemeni Al Qaeda operations director Fahd Mohammed Ahmed Al-Quso, who was wanted for the bombing of the USS Cole in 2000.
Quso, who was 37, had a $5m bounty on his head according to CIA officials.