Kremlin denies claim Sergei Skripal asked Putin for pardon

The attempted assassination sparked a diplomatic crisis between Russian Federation and Britain, which has been supported by its allies in apportioning blame to the Kremlin.

Russian Federation denies any involvement in the poisoning of Sergei and Yulia Skripal and is continuing to suggest that "military grade poisons" were being developed at the British defence laboratory at Porton Down.

The Porton Down chief executive, Gary Aitkenhead, told the BBC: "We have got the highest levels of controls, of security, around the work that we do here". Later, Prime Minister Theresa Mey stated that responsibility lies on Russian Federation, and the investigation confirmed the use of the nerve gas, produced in Russian Federation.

But the letter has sparked outrage, with Salisbury MP and Treasury Minister John Glen telling the Mail on Sunday: "It is a pathetic attempt to try to regain respectability when the ambassador knows full well Russian Federation is behind what happened in Salisbury".

He said: "In 2012 he called me".

Skripal was accused of working for MI6 over several years, in particular disclosing the names of several dozen Russian agents working in Europe. He denied he was a traitor.

According to Mr Timoshkov, his friend, who he had known since school, did not see himself as a traitor as he had sworn an oath to the Soviet Union.

He said: "Many people shunned him. His mother, brother and other relatives were (in Russia)". "His classmates felt he had betrayed the motherland", he said.

Alexander Vakovenko wrote: "I would like to express my honest gratitude to you for your bravery when reacting to the assault on two Russian nationals, Sergei and Yulia Skripal, on 4 March in Salisbury, who I hope will get well soon too".

Moscow's denial of the letter comes as Russia's ambassador to the United Kingdom wrote to Detective Sergeant Nick Bailey, who was recovering in hospital after being exposed to novichok whilst investigating the case.

Alexander Yakovenko also wrote to DS Bailey, who has said his experience was "completely surreal".