Bomb plot: toll could have been thousands

The terrorist masterminds behind the bomb plot wanted the carnage to overshadow that of the 9/11 attacks.

Prosecutors claimed thousands of people would have died in an unstoppable wave of suicide bombings on flights from Heathrow to North American cities.

It was alleged that the terrorists targeted up to seven flights, all scheduled to depart within hours of each other, making it impossible for the authorities to intervene.

Today the jury convicted ringleader Abdulla Ahmed Ali, Assad Sarwar and Tanvir Hussain conspiring to kill hundreds of people in a terrorist bombing campaign involving home-made liquid bombs used to attacks British targets including Heathrow Airport's terminal three.

The jury rejected the prosecution claim that Ali was responsible for an airline bomb plot, discarding evidence that he intended to target passenger jets flying from London to major North American cities with suicide attacks.

But police were convinced at the time that there was a viable airliner bomb plot,

Detectives discovered the al Qaida-inspired cell created ingenious liquid bombs which they believed were disguised as soft drinks to beat airport security.

In the chaotic hours that followed a wave of arrests in August 2006, aviation security chiefs implemented stringent new baggage restrictions.

Almost all liquids were banned from passenger hand-luggage, wrecking the travel plans of thousands of travellers and changing the face of air travel forever.

As time passed the restrictions were eased but a tight security regime remains in place and liquids in carry-on bags are limited to 100ml.

Counter terrorist police believed a senior member of the cell was preparing to test security with a dummy run transatlantic flight within days of their arrest.

A massive round-the-clock surveillance operation and a bug hidden in the gang's Walthamstow bomb factory gave detectives a ringside seat as the plot unfolded.

But several arrests in Pakistan and an intercepted text message encouraging the conspirators to act convinced police they must intervene.

The new information led police to mount a huge arrest and search operation on the night of August 9 2006.

The ensuing 24 arrests marked the turning point of what was to become the biggest counter terrorism investigation in British history.

The £30 million inquiry, codenamed Operation Overt, began in May 2006 when MI5 agents focussed their attention on the activities of Abdulla Ahmed Ali.

The operation quickly expanded as it became clear Ali was linked to a large circle of potential extremists, both in Britain and Pakistan.

Police believe he was given the blueprint for the plot during several visits to Pakistan where he met top al Qaida fixers.

Detectives discovered the shadow of extremist godfathers in Pakistan loomed large over every aspect of the conspiracy.

One of them, al Qaida militant Abu Obaidah al-Masri, who died earlier this year, may have been behind both Ali's plot and July 7.

Pakistani intelligence sources said the Egyptian-born militant specialised in recruiting and training British Muslims for attacks at home.

Furthermore, phone records linked Ali to July 21 ringleader Muktar Said Ibrahim and police cannot rule out they met in Pakistan.

Records showed conversations between the two men stopped between December 2004 and May 2005, possibly because they were together.

Two of the July 7 conspirators, Mohammad Sidique Khan and Shehzad Tanweer, also travelled to Pakistan during this period.

The July 21 and July 7 plotters used hydrogen peroxide-based bombs similar to those Ali's gang was planning to deploy.

Meanwhile in Walthamstow, High Wycombe and the West Midlands, dozens of surveillance teams watched and recorded key conspirators 24 hours a day.

They looked on as members gathered materials, identified their targets and tried to recruit footsoldiers.

Ali was watched visiting shops including Tesco, B&Q and Ikea to collect materials while Sarwar stockpiled chemicals in woodlands near his home.

Computer records revealed members also considered other mainland targets, potentially for a second wave of attacks.

Among them were gas terminals and oil refineries, Canary Wharf, internet service providers, London's electricity grid and various UK airports.

Several members experimented with 500ml Lucozade and Oasis bottles that would be injected with highly-concentrated hydrogen peroxide.

Police believed the bombs would have been assembled in flight, sparked by a detonator concealed inside cheap batteries and detonated with the flash from a disposable camera.

In the final days, officers listened in as some members recorded martyrdom videos, threatening further attacks against Western targets and non-Muslims.

But there were still fears among senior ranks that undetected members of the east London cell might exist with an unknown hoard of explosives.

One counter terrorism source said police were confident they "ripped the heart out" of an operation, which may have been launched within weeks.

He said: "From intelligence sources we were just aware it was likely towards the end of that week someone may try to travel on an aircraft across the Atlantic.

"That was something I was not willing to contemplate because it was too risky. The plot was coming to its denouement. One of the main leaders was going to travel.

"We are satisfied we arrested the key individuals and key conspirators in this plot and disrupted the attack."