Page "Double-Cross System" Paragraph 4

The agents were not difficult to spot-a task made still easier by the cracking of the German's Enigma encryption.

MI5, with advance warning of infiltration, had no trouble picking up all of the spies sent to the country.

Writing in 1972, John C. Masterman ( who would later head the Twenty Committee ) said that by 1941 MI5 " actively ran and controlled the German espionage system in United Kingdom.

" It was not an idle boast ; post-war records confirmed that no Abwehr agents went unnoticed.