Two of the London bombers travelled to Pakistan together last November and spent almost three months there, it emerged yesterday, pointing towards close links between the UK extremists and their Pakistani counterparts.
Pakistani officials released footage showing Mohammad Sidique Khan (30), the man suspected of leading the London cell, arriving from Britain at Karachi airport on the same Turkish airlines flight on November 19th last year as Shehzad Tanweer (22). The two stayed in Pakistan until February 8th before flying back to London together, immigration officials said.
Another of the July 7th bombers, Hasib Hussain (18), arrived separately in Karachi on July 15th last year.
Investigators are convinced that Tanweer met at least one senior militant - Osama Nazir - during a previous trip to Pakistan in 2003.
They also now believe that one or more of the London bombers, whose attacks on three tube trains and a bus claimed at least 56 lives, met a second militant, Zeeshan Siddiqi. Siddiqi, arrested in Pakistan two months ago, is associated with several radical groups.
Khan, a teaching assistant and respected figure in his Leeds community who is thought to have played a dominant role in the bomb plot, may have introduced Tanweer to contacts in Pakistan's thriving militant scene.
The revelation that three of the four bombers visited Pakistan so recently bolsters the belief that they had overseas militant links.
There were also unconfirmed reports yesterday that Khan, who police believe blew himself up on an underground train at Edgware Road, flew to Israel for 24 hours in 2003, where one Israeli newspaper suggested he may have helped plan a suicide bombing there.
Khan arrived in Israel on February 19th, 2003, and left the next day. The Israeli daily newspaper, Maariv, said he was suspected of helping two fellow Britons of Pakistani descent to plot a suicide mission at Mike's Place bar in Tel Aviv on April 30th, killing three Israelis.
In Pakistan, investigators are now gradually piecing together a clearer picture of Tanweer's and Khan's movements. They stayed at a hotel in Karachi's central Saddar area for a week before leaving for Lahore by train, a Pakistani newspaper, the Daily News, reported yesterday.
Pakistani officials now believe that Tanweer "shopped around", visiting several different radical madrasas. Detectives are also certain he spent time in Faisalabad, two-and-a-half hours' drive from Lahore, and a centre for radical Sunni activists.
Experts believe that only two Pakistani militant groups would have had the expertise and international resources to assist in an elaborate suicide operation in Britain - the banned Sunni group Lashkar-e-Tayyba and the Jaish-e-Mohammad (Army of Mohammad).