The former husband of alleged Russian spy Anna Chapman spoke today of his suspicions that she was being "conditioned" by shadowy contacts during their marriage.
The flame-haired 28-year-old is one of 11 people accused by the United States of working as secret agents for Russia's intelligence service, the SVR.
Alex Chapman, 30, from Bournemouth, Dorset, was married to the Russian, maiden name Kushchenko, for four years before they divorced in 2006.
Trainee psychiatrist Mr Chapman, who said he was quizzed by a Security Service officer on Wednesday about his relationship with Chapman, told the Daily Telegraph that his ex-wife's personality unexpectedly changed during their time together.
He explained: "There was such a dramatic change in the way she thought and the way she went about things, I felt I hardly knew her any more.
"It was like someone having a mid-life crisis, but in their 20s. She would arrange to go out but when I said I would join her she told me not to bother because they would all be speaking Russian. She was adamant I wasn't to meet them.
"She had never been materialistic during the years we were together, but in 2005 and 2006 after she started having these meetings with people she referred to as 'Russian friends'. She was transformed into someone with access to a lot of money, boasting about all the influential people she was meeting."
The Foreign and Commonwealth Office (FCO) said it is looking into Ms Chapman's connections to Britain.
But the department refused to comment on whether it was investigating the possibility that she spied against the UK while living here.
Mr Chapman told the paper that he did not believe his ex-wife was working as a spy in the UK but suspected she had been conditioned towards that end.
He said: "When she was still living in London she fell in with a group of people who had a lot of influence.
"She would go to film premieres and became arrogant and obnoxious, always going on about powerful people she was meeting."
Chapman, who was arrested in New York on Monday, worked in London between 2003 and 2007.
During their marriage, the couple rented a flat in Stoke Newington, north London.
Mr Chapman met the Russian in September 2001 when she was an economics student at Moscow University.
He told the paper: "Anna was the most beautiful girl I'd ever seen in my life.
"I plucked up some courage and went over to her and said 'I'm sorry, but you're the most gorgeous girl I've ever seen'. She turned round and looked at me and said 'My God, so are you'."
Mr Chapman said his former wife sounded "distant" when he last spoke to her four weeks ago.
Another of the alleged Russian agents arrested by US officials in Monday's raids was Tracey Lee Ann Foley, who is accused of travelling on a fake British passport.
The FCO said it was investigating the matter but remained confident that the British passport was "one of the most secure documents of its kind".
Officials in Dublin are also looking into claims that a false Irish passport was to be used by a member of the alleged spy ring.
Members of the alleged ring were said to have sent information from America back to the Kremlin in a plot which could have come straight out of a James Bond novel.
US court papers lift the lid on techniques such as a new hi-tech spy-to-spy communications system allegedly used by the defendants: short-range wireless communications between laptop computers - a modern supplement for the old-style dead drop in a remote area - and high-speed burst radio transmission.
The defendants are all accused of conspiracy to act as unlawful agents of a foreign government.
Eight also face a charge of conspiracy to launder money.