A Royal Navy petty officer has been jailed for eight years today for trying to disclose the secret movements of British nuclear submarines.
Edward Devenney, 30, began plotting the treachery after he was passed over for promotion.
He was caught by an MI5 sting earlier this year after meeting two intelligence officers posing as Russians.
He pleaded guilty to breaching the Official Secrets Act by gathering classified information and misconduct in public office.
ITV News' Crime Correspondent Jon Clement reports.
Sentencing him at the Old Bailey, Mr Justice Saunders said Devenney knew what he was doing when he met the 'spies'.
He did supply details of movements and operations carried out and to be carried out by nuclear submarines.
I am satisfied that in the wrong hands it was capable of affecting the operational effectiveness of nuclear submarines.
This is a very serious case. The defendant was prepared to betray his country and his colleagues.
During the trial, the court had heard that Devenney rang the Russian Embassy in November last year, after what he said was a 12-hour drinking binge.
He thought he had been treated badly by the Royal Navy because he was not promoted to chief petty officer.
Two days later, he managed to get into a locked safe on board HMS Vigilant and take three photographs of part of a secret code for encrypted information.
The judge said: "The photographs could, with other information, have led to the breaking of the code."
Outside court, Devenny's solicitor Richard Cannon read a statement on his behalf, which said:
I am deeply sorry for the hurt and shame that I have brought on my family and loved ones.
Prior to these events I gave the Royal Navy 11 and a half years of service and I deeply regret my actions and the effect they have had on the Submarine Service and colleagues.
Mari Reid, unit head for the CPS counter-terrorism division, said:
This was a classic story of betrayal.
Edward Devenney was employed by the Royal Navy to protect this country from potential threats to our security.
Instead, he pursued a course of conduct likely to put his country at risk.
We rely on the men and women of our armed forces to keep us safe.
It is hard to imagine a greater breach of that role than Devenney's actions.