Ekaterina Zatuliveter was in Gatwick Airport in August last year, on her way back from a birthday party in Croatia, when her path first crossed that of the UK's security services.
At her flat was a diary detailing her relationships and affairs with several European diplomats, and the Liberal Democrat MP Mike Hancock. MI5 believed she was a spy, sending information back to Moscow gleaned from her role as researcher for Mr Hancock, a member of the Defence Select Committee.
But after a year-and-a-half of an intense and humiliating legal dispute, the 26- year- old Russian was told that she was not a spy, after all. Having faced deportation, Ms Zatuliveter is now at liberty to remain in the UK. After the hearing, she said she was "very happy" but was prevented from speaking further by a minder from the South West News Service, which covers Mr Hancock's Portsmouth constituency, amid speculation she is to sell her story to a newspaper.
A panel of the Special Immigration Appeals Commission, which included the former MI5 director general Sir Stephen Lander, ruled that suspicions about Katia Zatuliveter passing on secrets while working for Mr Hancock had been reasonably held but were wrong.
In a hearing in October Ms Zatuliveter put her case in open court, while the Home Secretary Theresa May and other security officials made their submissions behind closed doors, preventing Ms Zatuliveter from knowing the details of the case against her. After the verdict her solicitor, Tessa Gregory, said her client had been living a "Kafkaesque nightmare" for the last year. "Our security service is supposed to be responsible for protecting us against serious threats.
"It is therefore extremely worrying that they have chosen to waste their time, at great public expense, needlessly and unfairly pursuing an innocent young woman. Their case was built entirely on speculation, prejudice and conjecture. It was amateur and poorly researched." The tribunal heard how she first met the 65-year-old MP at an an inter-parliamentary conference on Russia's relations with the EU and Nato in 2006, and began a four-year affair with him shortly after. It was only on her arrest in December 2010 that she learnt he was still married.
The tribunal also heard details of three other relationships with European diplomats, among them a Dutch diplomat and a Serbian.
The Home Office said it was disappointed with the ruling.
Spooks: What they did next
Kim Philby One of the "Cambridge Five", Philby escaped to the Soviet Union in 1963 after he was exposed as feeding information to the Russians from his senior role in the British intelligence. Received a hero's funeral in Moscow in 1988.
Anna Chapman Arrested along with nine other Russians in New York last June, and pleaded guilty to a charge of conspiracy to act as an agent of a foreign government. She was repatriated to Moscow, and his since posed in her underwear for Maxim magazine.
Sergei Skripal The former Russian officer began working for MI6 in the 1990s, before his conviction in Russia for spying in 2006. He was freed in July last year as part of a spy swap between Russia and the US. The freed American spies flew to the States, but Mr Skripal was dropped off in the UK, and has been living here since then.