One millimetre from carnage

The men who brought Islamist terror to Scotland were just a millimetre away from causing mass murder. It was only fractions - a tiny gap in a wiring circuit, a window shut tightly - that proved the margin between life and death and set police on the trail of Bilal Abdulla and Kafeel Ahmed as they prepared for martyrdom at Glasgow Airport.

When the Mercedes car bombs set by the Iraqi doctor and the Indian engineering student in the West End of London failed to explode, they left police with crucial evidence. But it also led them to the realisation that they might have only minutes to act before another attack. Counter-terrorism officers traced the bombers to 6 Neuk Crescent in Houston, Renfrewshire, not far from Paisley's Royal Alexandra Hospital where Abdulla worked as a diabetes doctor.

By 6am on the morning of the airport attack, Strathclyde Police had set up surveillance of the house, arriving less than a hour after the bombers left. By then, Abdulla and Ahmed were heading north to Loch Lomondside where they would spend the morning of June 30, 2007.

Just as the paraphernalia of modern terrorism found at Neuk Crescent was prosaic - the Autotrader car magazine, equipment from B&Q stores - the police detection technology was highly efficient.

ANPR, or automatic number plate recognition, linking 3000 road cameras to a database, was able to track the two bomb cars towards Scotland. Mobile phone data from four intact Sim cards left at the scene of the London attacks, gave police a wealth of material.

When Ahmed sent a text message to his brother in Liverpool a 1.47pm, police traced it to a mobile phone mast serving the Loch Lomond area. If it had been in a city, the caller would have been pinpointed exactly. Instead, a wide area was covered by a single mast. As police raced to the main A82 road on the western shore, on the tranquil eastern banks at Milarrochy the bombers were setting off on their suicide mission.

The bombers - independent, intelligent and invisible - were the perfect sleeper cell. The internet was an essential tool in the bomb factory, with the terrorists spending hours researching improvised vehicle bombs using gas cylinders.

Abdulla, who portrayed himself in court as a man traumatised by a lifetime of war and invasion in Iraq, is believed by security services to have joined militia fighters in Baghdad as the city descended into chaos after the 2003 invasion. Security services think he was sent to London by senior insurgent figures in Iraq who saw his British passport as his greatest weapon.

Ahmed, whose family live in Bangalore, India, was inspired by fighters in Kashmir and the pair became kindred spirits when they met in Cambridge. In their wills, Abdulla and Ahmed admitted acting on behalf of a mystery "emir" (leader), but police are reluctant to name any suspect in the UK.

Police have not revealed whether they traced any communications between Abdulla and other figures in Iraq. Nevertheless, just hours before the attacks, one chat room often used by al Qaeda supporters hosted the prophetic message: "Today I say, Rejoice, by Allah, London shall be bombed".' For all his intelligence, and his extremist commitment to his cause, Abdulla had chosen to train as a healer - so was ill-equipped when he turned killer. "Their lack of expertise was their undoing," said a senior investigating officer.

The Glasgow Jeep bomb has been dismissed as a frightening but amateurish attempt at a mass explosion device. The London bombs simply fizzed because of faulty wiring and the fuel-to-air mixture. Closing a tiny gap and opening a window slightly would have transformed the attacks, making the difference between a lucky escape for hundreds and mass murder.