One of the July 7 London suicide bombers had links to a British man who planned a suicide attack on Tel Aviv two years ago, raising fears that the network of Islamist hardliners is wider than first thought.
The Independent on Sunday has learnt that Mohammed Sidique Khan, 30, who carried out the Edgware Road bombing, was friendly with Omar Sharif, one of two Britons who plotted a joint suicide attack in Israel in April 2003.
The disclosure comes as police continued their investigation yesterday into possible links between the four suicide bomb attacks on 7 July and the devices used in the botched attacks last Thursday.
One theory is that the explosives used last week were either part of the same batch as those used on 7 July or made to the same formula - using commonly available chemicals to create the home-made explosive acetone peroxide.
Security experts believe Thursday's devices may have failed to explode because the explosives had degraded. Acetone peroxide is known to deteriorate quickly.
Police now have samples from last Thursday's attacks to compare to unused explosives found in Leeds 12 days ago.
Meanwhile, police attempts to uncover the 7 July bombers' network of terrorist contacts are focusing on Khan's relationship with Sharif.
Despite pre-recording a "suicide bombers" video in advance, Sharif failed to detonate his device; but his co-conspirator Asif Hanif carried out his attack, claiming three lives at Mike's Place in Tel Aviv.
Sharif ran off, but his body was later washed up on a nearby coast.
It is now thought that Sharif's family lived in Leeds before they moved to Derby and that he went to the same mosque in Beeston as Khan, who was brought up in the area before moving to Dewsbury.
A possible link emerged last week after it was disclosed that Khan had visited Israel for a day in February 2003, raising suspicions that he had been on a reconnaissance trip for Sharif and Hanif, both of Pakistani descent.
As the Independent disclosed last week, Khan is also believed to be linked to al Qaeda.
He was identified by a Pakistani-American computer expert, Mohammed Junaid Babar, 29, who was arrested after attending al Qaeda summit meetings in Pakistan.
These links strengthen suspicions that Khan was the dominant influence on the other two bombers from Leeds, Hasib Hussain, 18, who carried out the No 30 bus bombing, and Shahzad Tanweer, 22, who carried out the Aldgate Tube attack.