Sergei Skripal has been named as the man who, along with a woman, was found unconscious in a shopping centre in Salisbury.

The 66-year-old had apparently been poisoned and is in hospital, where he is described as being in a critical condition.

Mr Skripal, who has an address in Salisbury, served in Russian military intelligence as a colonel until 1999.

After that he worked at the country’s foreign ministry until 2003.

But he was arrested in Moscow a year later and confessed to having been recruited by British intelligence in 1995.

He said he had given information to British intelligence about Russian agents in Europe in return for around $100,000.

During his trial, Russian media quoted the country’s security agency as saying the damage from Skripal’s activities was comparable to that caused by Oleg Penkovsky, a colonel who spied for the US and Britain and was executed in 1963.

In 2006, Mr Skripal was convicted of spying and sentenced to 13 years in a high security prison.

But he was released in 2010 and given refuge in the UK as part of a spy swap between Russia and the US.

Ten Russians were expelled from the US and Mr Skripal was one of four Russians released, with the two groups being swapped on the tarmac at Vienna’s airport.

One of the Russian agents released by the US in the deal was Manhattan socialite Anna Chapman, who had been married to a British man and lived in London for several years.

The plane carrying the group from Russia is thought to have landed at RAF Brize Norton and at the time the Foreign Office refused to say whether the men would remain in the UK.

The other three Russians released in the deal were Alexander Zaporozhsky and Igor Sutyagin, both convicted of spying for the US, and Gennady Vasilenko who had been jailed for illegal weapons possession.

Between then and his suspected exposure to an unknown substance, however, Mr Skripal seemed content with a quiet life in the pretty cathedral city of Salisbury.

Mr Sutyagin later told The Guardian that Mr Skripal had talked about his family, adding: It seemed to me it was his family which was his major joy.
(c) Sky News 2018: Who is Russian double agent Sergei Skripal?