Michael Bettaney was a heavy drinker whose unstable behaviour had been noted but never raised questions long before his ill-fated attempts to pass British intelligence secrets to the Russians in the 1983.

The M15 officer turned traitor was a patriot who joined the security services in 1975 after being rejected by the civil service.

During his eight-year career he served in Northern Ireland and was promoted in 1982 to K branch, the section dealing with counter-Soviet intelligence.

He was initially branded a high flyer but investigations after his conviction revealed a man who was violent, unpredictable and abusive towards women.

His drinking was a constant, if overlooked, problem and in 1982 he pleaded guilty before London magistrates to being drunk and disorderly in a West End street.

While working for the Russian section Bettaney seems to have reassessed his basic beliefs.

His religious enthusiasm waned and he joined the Labour Party, then went on to embrace Marxism. He told friends he believed the Soviet system was superior to that of the West.