Chapman lived in Britain for almost five years and her CV paints a picture of a high-flying existence working in a string of top London companies before launching her own international property firm with a multi-million dollar turnover. The 28-year-old boasted that her work in the capital brought her into contact with Warren Buffett, the billionaire US investor, but last night it emerged that many of her claims were exaggerated. By the time she moved to New York two years ago she described herself variously as a property entrepreneur and a financial investments trader. She was among 10 Russian citizens arrested in the US on Monday accused of adopting false identities to spy on the West as "sleepers". MI5, which carries out Britain's counter-espionage work, is understood to be helping the Americans in their investigation. It is also assessing whether there could be security implications for Britain after details emerged of Chapman long-standing connection with this country.