BRITISH and American special forces held a secret training exercise last month to prepare for terrorist “dirty bomb” attacks on London landmarks, The Sunday Times can reveal.
Bomb disposal experts from the SAS and Special Boat Service (SBS) worked with elite operators from the American military’s Delta Force and Navy Seals and the FBI.
The aim was to test how security forces would cope if faced with a new generation of complex improvised explosive devices (IEDs).
“These bombs made the stuff we’ve seen in Afghanistan look like toys
During the exercise up to 10 four-strong teams raced to defuse bombs packed with “notional” high explosives, chemicals and radioactive material that, if real, had the potential to cause hundreds of casualties.
At least four venues in central London were used during the drill. The teams wore plain clothes and used civilian cars or public transport.
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A range of devices, which looked like bombs but contained no dangerous material, were placed at targets including Lord’s cricket ground, a disused building near Lambeth Palace and buildings next to the MI6 headquarters overlooking the Thames.
Defence sources said the IEDs were far more advanced than those used against British troops in Iraq and Afghanistan.
It is understood that one of the mock bombs was a sophisticated suicide vest with a timer that had to be neutralised before the device could be defused.
Another scenario involved a “bomb” supposedly packed with radioactive material and fitted with anti-tampering devices. The teams were told that cutting the wrong wire would detonate it.
The exercise, which took place over several days in late February, was called Kirchhoff’s Impedance after Gustav Kirchhoff, a German physicist who worked on electrical circuits. Impedance is a measure of the resistance that a circuit presents to a current.
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On February 25, five teams of specialists had the task of disarming devices placed in the Grand Stand at Lord’s.
The ground had agreed to host the exercise after being approached by the Ministry of Defence and the Metropolitan police.
“High-profile targets were chosen to bring more drama to the exercise,” a source said. “The bombs were incredibly sophisticated.”
The source added: “Once the bomb was discovered the teams had to make an assessment of the threat to both the bomb disposal officer and the building.
“They had to establish what its primary function was — either an explosive or dirty bomb, designed to contaminate an area.
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“The teams were working against the clock but it wasn’t just a race against time. They also had to make the right decision and go through the whole threat assessment process.
“Everyone was working outside their comfort area. It was designed to test the teams in ways they had never been tested before. These bombs made the stuff we’ve seen in Afghanistan look like toys.”
The bomb exercise, which was separate from a drill last week in which the emergency services practised their response to an Underground train disaster, was run by the SAS and SBS.
Their US counterparts were invited because UK and US special forces are often deployed on missions together. The SAS has created two new units to deal with the global IED threat.
The exercise was arranged after intelligence from British and American agencies suggested that Islamist terrorists were trying to develop a new generation of bombs.
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Sources say terrorist groups have been recruiting chemists and electronic experts to build complex IEDs.
Hamish de Bretton-Gordon, a former commander of British chemical warfare forces, said he had inspected “quite a sophisticated” chlorine bomb in April, planted in an Indonesian shopping centre by a jihadist believed to have returned from Syria.
“It had several detonators and it struck me as not something you can just learn off the internet and knock together . . . The fact that so much effort is going into this [training] should really reassure people that we recognise it’s a threat, although probably not a huge threat,” he said.
James Clapper, the director of US National Intelligence, warned last month that Isis “would like to use chemical weapons” in an attack on America. It also emerged that Iraqi authorities were searching for “highly dangerous” radioactive material that went missing from a US-owned storage facility in Basra last November.