There are any number of stories that even a cursory look will bring you

According to former inmates, there were 52 kinds of torture used in the prison. Historian and Gulag researcher Lidia Golovkova, author of the book Sukhanovskaya Prison: Special Facility 110, compiled a detailed list of the ‘methods of interrogation’ used there. ‘It was regarded as the most horrific prison in the whole of the Soviet Union’, she told me. ‘The usual, simplest method used was beatings, which could go on for days, with interrogators working in shifts. They would beat prisoners on the most sensitive parts of their bodies; it was known as ‘threshing the rye.’ The second most common method was sleep deprivation, which could go on for 10-20 days. During interrogation, prisoners were often made to sit on a leg of an upturned stool, so that the slightest accidental movement would send the leg into their rectum.

‘Another form of torture was known as the “Sukhanovka Swallow”, where inmates were trussed up with a long towel that was forced between their lips like a horse’s bridle and then pulled down behind them and tied under their feet. You would think no one could stand this for more than a few seconds, but its victims were left like that for days on end. There were also overheated punishment cells, so called “tallow-boilers”, or in winter, prisoners could be dumped in barrels of icy water. Other methods of persuasion included prisoners having needles and pins forced under their fingernails, their fingers being crushed in a door, or being forced to drink their interrogator’s urine.’

I asked Golovkova whether people sometimes held out and refused to sign confessions even after torture. ‘That was very rare. The pain of the beatings and torture was so excruciating that 50-year-old generals would forget themselves and start crying for their mothers. General Sidyakin lost his mind and howled in his cell like a dog. Many prisoners were sent off to psychiatric hospitals for compulsory treatment immediately after their interrogation.

‘I only know of one documented case of a prisoner who refused to confess despite being tortured. He was Mikhail Kedrov, a member of a Moscow aristocratic family who became a Leninist Bolshevik and member of the Cheka, [the first incarnation of the Soviet secret police apparatus]. In 1939, Kedrov, with his son Igor and one of his friends, who also worked for [what in the 1930s was renamed] the NKVD, wrote a letter about abuse of power in the Security Services, and all three were immediately arrested and interrogated for 22 hours or more. The two young men were shot first, but Mikhail Kedrov refused to confess to anything, no matter what tortures he was subjected to. Amazingly, a court found him not guilty of any crime, but he was still not released from prison; and when the USSR entered the Second World War in 1941, he was executed on the direct orders of Lavrenty Beria.