Former SAS member Sir Ranulph Fiennes calls his book a mixture of 'fact and fiction' [GETTY]

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The “Boston Brakes” technique, allegedly developed by the CIA, involves planting remote control devices in the victim’s car so the assassins can cause it to crash.

After the accident the controls are removed by stealth, leaving no trace.

Sir Ranulph, a former SAS member, details the method in his book The Feather Men, which he calls a mixture of “fact and fiction”.

He describes a real accident in 1986 involving Air Marshal Sir Peter Horsley, former equerry to Prince Philip.

As Sir Peter was driving down a dual carriageway to Plymouth, his BMW inexplicably swerved into the path of an oncoming car, killing the other driver.

Sir Peter survived and investigated the crash himself. He was convinced he was a victim of the “Boston Brakes” method and that his car was caused to swerve by killers following him in a Volvo.

Afterwards they removed the controls.

In his book, Sir Ranulph claims the attempt was carried out by a hit squad called The Clinic but invites his readers to decide what is real and what isn’t.