[4] Merkulov was transferred to Moscow in August 1938, shortly after Beria had been chosen by Stalin to take over control of the NKVD from Nikolai Yezhov.

When Beria took over as head of the Main Directorate of State Security (GUGB) on 29 September 1938, he chose Merkulov as his deputy.

[5] In 1939, he was elected a member of the Central Committee of the Communist Party of the Soviet Union Merkulov interrogated Yefim Yevdokimov, an associate of Yezhov who had been under arrest for five months but had refused to cooperate.

In September 1939, following the pact between the USSR and Nazi Germany, Merkulov was sent to Ukraine to supervise the incorporation of territory seized from Poland.

[7] When almost 22,000 Polish officers were executed in the famous Katyn massacre in spring 1940, Merkulov headed the 'troika' who signed off the death sentences.

[9] In his role as head of foreign intelligence, Merkulov travelled with Molotov to Berlin in November 1940, to have breakfast with Hitler.

Merkulov made the officer who struck the blow, Lev Shvartsman apologise – for causing blood to spill on the carpet.

[14] In November 1944, Pavel Fitin reported: Despite participation by a large number of scientific organization and workers on the problem of Enormoz in the U.S., mainly known to us by agent data, their cultivation develops poorly.

[1] The author Nikolai Tolstoy, in his Victims of Yalta (1977), recounts Merkulov speaking to the imprisoned Cossack general Pyotr Krasnov in the Lubyanka in 1945.

(The report is the testimony of the general's son, Nikolai Krasnov, who was also present and later released from the Gulag under Nikita Khrushchev's 1955 amnesty.)

We'll blow them to blazes with all their kings, with all their traditions, lords, castles, heralds, Orders of the Bath and Garter, and their white wigs.

This was a setback for Beria, who lost control of the police apparatus to a younger rival, Viktor Abakumov, while Merkulov was unemployed for over a year.

He wrote a long letter denouncing Beria as an ambitious schemer, but claiming that despite having known him for 30 years, Merkulov had only now realised that he was a criminal.

It was more like a piece of fiction ... To my deep regret, since I had trusted him, Merkulov turned out to be deeply implicated in some of Beria's crimes.