The identification of Alexander Petrov and Ruslan Boshirov as the two GRU assassins believed to be responsible for the attempt on the lives of Sergei and Yelena Skripal in Salisbury takes us back to the darkest days of the Cold War, when trained KGB killers were deployed to hunt down defectors – often using theatrical methods to eliminate them.

Nikolai Khokhlov – a KGB agent who defected to the United States in 1954 – survived a near-deadly dose of radioactive thallium that was slipped into his coffee after giving a speech in Frankfurt. The unusual tradecraft employed in March, involving a fake Nina Ricci aerosol, is also reminiscent of the ingenious cyanide gas-gun developed by the KGB which Bogdan Stashinsky used to assassinate two Ukrainian nationalist leaders in the 1950s. A ricin pellet gun disguised as an umbrella was used against Georgi Markov in 1978.

The GRU itself has a long Cold War pedigree. It is the unreconstructed successor to the Fourth Department of the General Staff of the Soviet Red Army, originally created by Trotsky, and is based at its old headquarters on the edge of the Khodinka military airfield in Moscow, known as “the aquarium”. It is an elite, highly disciplined organisation that suffered few defectors during the Cold War, in comparison to its rival, the KGB. According to one successful GRU defector, Vladimir Rezun, now in hiding, new GRU recruits endure a film depicting the execution of a GRU traitor being fed into an incinerator, strapped to a stretcher.

The GRU supplies defence attachés across the world, staffs the Spetznaz special forces and assigns selected personnel to undertake extra-judicial killings. And the past record of its involvement in murders highlights not just its boldness in operating overseas, but also the reception the two Salisbury poisoners are likely to have received in Russia.

Take the murder of Zelimkhan Yandarbiyev, the former Chechen leader, in February 2004. He was killed with his two bodyguards when a bomb detonated under his SUV in Doha as they drove home from a mosque. Suspicion quickly focused on two men of Slavic appearance who had been seen carrying a plastic bag in the Mosque’s carpark.

Six days later, the Qatari police arrested three Russians including two GRU officers, who were convicted of the murder in June 2004. In their confessions – which they alleged had been extracted under torture – they identified the Russian defence minister, Sergei Ivanov, as the person who had issued them with the orders to kill Yandarbiyev. Six months later they were repatriated to Moscow to serve the remainder of their sentences, but instead received a heroes’ welcome and were released.

The Kremlin, which claimed that the two GRU officers had been sent to Qatar on a legitimate anti-terrorism liaison assignment, hired some very high-priced lawyers to defend them, including the firm founded by President Vladimir Putin’s chief of staff. Such an intervention indicates the level of sponsorship enjoyed by the GRU from the Russian leadership.

Nigel West is the author of Cold War Spymaster (Frontline)