Sergei Skripal once was a colonel in a Russian military intelligence service. In the early 1990s he was recruited by the MI6 agent Pablo Miller. He continued to spy for the Brits after his 1999 retirement. The Russian FSB claims that the British MI6 paid him $100,000 for his service. At that time a Russian officer would only make a few hundred bucks per month. Skripal was finally uncovered in 2004 and two years later convicted for spying for Britain. He was sentenced to 18 years and in 2010 he and other agents ware exchanged in a large spy swap between the United States and Russia. Skripal was granted refuge in Britain and has since lived openly under his own name in Salisbury. His wife and his son died over the last years of natural causes. The only near relative he has left is his daughter who continued to live in Russia.
http://www.moonofalabama.org/2018/03/spy-posions-spy-and-the-anti-trump-campaign.html