The failed chemistry of a city-wide terror plot
In short: On July 21, 2005, four simultaneous bomb attempts paralyzed London's transport system. While the goal was mass casualties, the devices were plagued by poor manufacturing. Only the detonators fired, producing pops no louder than fireworks and leaving a city in shock but physically intact.
The attacks targeted three Underground stations—Shepherd's Bush, Warren Street, and Oval—alongside a bus in Haggerston. The perpetrators used an improvised explosive mixture of chapatti flour powder and concentrated liquid hydrogen peroxide, intended to be triggered by TATP charges. However, the primary explosives failed to detonate because of the low quality of the hydrogen peroxide obtained from various easily available sources. This chemical failure meant that only the detonator caps fired, resulting in small explosions and a distinct smell of vinegar or burning rubber. Witnesses reported a strange odor preceding the bangs by several minutes. The devices were packed into clear plastic food containers sold in roughly 100 UK outlets.
The aftermath was defined by high-tension manhunts and tragic errors. The Metropolitan Police described the search for four suspects as their greatest operational challenge. During this period, police mistakenly identified and fatally shot Jean Charles de Menezes, an electrician who was simply traveling to fix a fire alarm. Despite his innocence being confirmed on July 23, police initially propagated falsehoods about his behavior during the investigation. The manhunt began after CCTV images of four suspects were released on July 22. Police eventually arrested all four main targets by July 29 across London and Rome.
The psychological impact of these events varied significantly across demographics. A study conducted shortly after the July 7 bombings showed that while only 1% of Londoners felt they needed professional help, non-white and Muslim residents reported disproportionately higher levels of substantial stress. Seven months later, follow-up research indicated that while acute stress levels dropped, a more negative worldview persisted among many survivors. Research found that previous experience with terrorism was associated with lower stress levels. Conversely, those who thought they could have been killed reported higher distress.
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Sources
- Summary by Intellect · source: 21 July 2005 London attempted bombings
- Also: Psychological and behavioural reactions to the bombings in London on 7 July 2005: cross sectional survey of a representative sample of Londoners
- Also: Bombers attempt to attack London transit system | July 21, 2005 | HISTORY
- Also: The British Journal of Psychiatry — Enduring consequences of terrorism: 7-month follow-up survey of reactions to the bombings in London on 7 July 2005 · CC0 (metadata)
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