Today, four people were arrested in Montpellier on suspicion of plotting to attack an unspecified tourist destination in Paris. Buried in the news was the fact that investigators had found an explosive nicknamed the 'Mother of Satan' in their search of the plotters' residence.
This type of explosive, a favourite of Islamic State, was deployed in the terror attacks in Paris in November 2015 and Brussels last year. Yet we have heard little about this substance, or its incendiary nickame, until now.
The official name of 'Mother of Satan' is triacetone triperoxide (TATP), a chemical compound containing core ingredients of acetone and hydrogen peroxide. Because it does not contain nitrogen, explosive detectors often can't pick it up. The accessibility of the ingredients - such as bleach and drain cleaner - makes it attractive for Isis and terrorists operating in Europe.
TATP has been around for a long time - it was discovered in 1895 by a scientist called Richard Wolffenstein - but it took the best part a century for would-be terrorists to spot its potential. But then Palestinians began using it in the West Bank in the 1980s, according to the Times, and it was subsequently harnessed by Al-Qaeda and other extremist groups.
The four bombers in London on 7/7 had used TATP in their bombs, which were set off on major tube lines and a bus in Tavistock Square during rush hour, killing a total of 52 people and injuring more than 700. A similar explosive was used by Richard Reid - the “shoe-bomber” - who attempted to detonate a device on a flight from Paris to Miami.
The compound releases a huge force when it detonates but is also highly unstable, and several bombmakers have died in the process of making TATP devices - which might explain the sinister nickname. A US army official cited by the Washington Post said military forces rarely use it because of its inherent volatility.
Yet, for terrorists who want to cause as much carnage as possible and aren't too bothered if their bomb actually detonates en route to the target, it's easy to see why this malevolent compound appeals. The 'Montpellier four' may have been thwarted, but the Mother of Satan certainly hasn't been banished to hell.