In the summer of 2006, British intelligence agents intervened to dismantle a major al-Qaeda plot aimed at detonating liquid explosives on seven transatlantic flights. The planned attacks, which experts warned could have resulted in a death toll surpassing that of the September 11, 2001 attacks in the United States, prompted the largest counterterrorism surveillance operation in UK history, known as Operation Overt.

Two MI5 officers, working undercover, carried out a critical raid on an unremarkable flat in East London, believed to be a hub for the terror cell. Their goal was to gather evidence and install surveillance equipment to monitor the suspects’ activities. According to one agent involved in the operation, the mission was urgent and high-risk, as any mistake could have jeopardized the entire investigation.

Inside the flat, investigators discovered a range of materials linked to bomb-making, including empty soft drink bottles marked with brands like Lucozade and Oasis, jars containing batteries and a viscous liquid. Subsequent surveillance captured footage of suspects drilling into the bottom of bottles and injecting them with an explosive mixture of hydrogen peroxide combined with an orange-tinted additive. The devices were reportedly rigged to disposable cameras serving as detonators.

Recorded conversations and videos from the flat led MI5 to identify at least 24 individuals connected to the plot, including 18 additional suspects whose movements were closely monitored. Concern escalated when six of the suspects were observed filming martyrdom messages, suggesting the attacks were imminent. Nonetheless, MI5 delayed arrests to secure sufficient evidence to ensure successful prosecutions.

When one of the ringleaders, Abdulla Ahmed Ali, was observed researching flights bound for the United States, the situation gained international attention. U.S. officials, including then-President George W. Bush, urged swift action. The CIA’s tip-off that Rashid Rauf, a key figure suspected of orchestrating both this plot and the 2005 London transport bombings, was moving through Pakistan accelerated the timeline.

Following the CIA directive, British authorities launched coordinated raids on August 9, 2006, arresting 24 suspects across London, High Wycombe, and Birmingham. The subsequent legal process involved seven trials and retrials, costing an estimated £70 million.

In 2009, Ali, Assad Sarwar, and Tanvir Hussain were convicted of conspiracy to murder related to the liquid bomb plot, receiving minimum sentences of 40, 36, and 32 years respectively. Umar Islam was also found guilty of conspiracy to murder, with a minimum term of 22 years. Eight others were convicted of lesser offenses, while Mohammed Gulzar, described by authorities as the “superintendent” of the plot, was acquitted.

Rauf evaded capture in Pakistan after escaping custody but was killed in a U.S. drone strike in 2008 at the age of 27.

The intelligence gathered during Operation Overt led to airport security measures restricting liquids on flights, changes that remain in place globally. The agents involved have now detailed the operation in an ITV documentary marking the 20th anniversary of the plot’s foiling.