Yesterday, in the first part of a spine-tingling new series by top espionage writer BEN MACINTYRE, we revealed how a sex-mad Soviet agent posed as a Cotswolds housewife to run a cabal of Communist spies from her cottage.
Here, we tell how she delighted her masters and even Stalin himself with her access to the very heart of Britain s top-secret atom bomb research.
When housewife and mother Ursula Beurton in reality, Major Ursula Kuczynski of the Red Army, a Soviet spy who had conducted espionage operations in China, Poland and Switzerland landed at Liverpool on a ship from Spain in early 1941, MI5 already had its suspicions about her.