By Dominic Casciani
Rows over the jailing of Adolf Hitler's deputy became a key point of Cold War tension, papers reveal.
Hess killed himself inside Spandau prison at the age of 93
Rudolf Hess was held in Berlin's Spandau prison until his suicide in 1987, aged 93.
The documents show British governors fought Soviet attempts to turn the jointly-run jail into a "gulag" labour camp with just one prisoner.
France, the US, UK and Russia jointly managed the jail - and disputes over Hess led to bitter recriminations.
Hess had been in custody since flying to Scotland in 1941. Marginalised in the Nazi hierarchy with increasing mental problems, he thought he could strike a peace deal with Britain so Hitler could invade Russia unhindered. He ended up jailed for life at the Nuremberg war crime trials.
Spandau prison was jointly run which caused its own tensions
By the 1970s, he was the only Nazi left in Spandau and a humanitarian campaign had been launched to see him released.
The three western powers sympathised but could do nothing without the Soviet Union's agreement.
In files originally opened two years ago after a Freedom of Information request, National Archives documents show the stand-off reached a boiling point in 1974.
The Western powers fell out with Russia over Hess's health after doctors warned he could have cancer. The British wanted Hess taken for tests at their nearby military hospital. But the Russians told the Americans to pay for an x-ray machine in the prison instead.
The papers show how British governor, Robert de Burlet, began taking his Russian counterparts to task over "prisoner number seven", as Hess was officially known.
In one meeting, de Burlet demanded the Russians see sense.
"If you keep him in prison until he dies, you have created a martyr who would be remembered not for his own misdeeds but for the inhumane treatment which he himself suffered."
The Russian official, Romanovsky, privately conceded that he sympathised with the British position. But he said decisions over Hess were taken at the top and added: "I do not think that for us it will be possible to release him - the political difficulties are too great."
Neo-Nazis adopted Hess as a "martyr"
And so Hess's regime remained strict. Confined to a small badly-furnished cell, his requests for more relaxed rules led to petty and pointless political clashes.
The Russian governor began censoring large parts of Hess's letters to his wife. He ordered his guards to take Hess's glasses at lights out - a regulation that was never followed by the other powers.
When a Russian guard established that Hess had 13 photographs in his cell, rather than the regulation 10, three were removed - leading to another row in the governors' office.
Hess wrote himself a sign reminding himself to stand up in the presence of the Russian commandant. The three other powers said they didn't want an old man to stand.
The British became convinced the Russians wanted to turn Spandau into a western outpost of the "Gulag Archipelago" - the Soviet Union's forced labour camps.
Hess wrote a note reminding himself to stand for the Russian governor
In one incident, Hess saw some windfall plums in the prison gardens and wanted to take them inside rather than leave them to the birds. The Soviet guard said no - but was overruled by the British warder
Within days, the incident had escalated into a full-scale row between the four governors with the Russians accusing the British of breaching the original post-war agreement over war criminals and demanding reports and disciplinary action.
"We have what I consider a genuine case of mental cruelty," said Robert de Burlet.
"Whatever horrors the Germans had perpetrated in their concentration camps I do not want it to be said that we were following their example."
London urged him to resist attempts to tighten the regime and diplomatically endure lecturing from Russian generals, one of whom was frequently the worst for drink.
Hess's birthday passed with no sign of movement on release. And in a sarcastic editorial marking the occasion in Pravda - the Kremlin's official newspaper - explained why.
"The Hitlerite lieutenant must drink his retribution to the bottom of the cup," it said.