Edward Devenney was apparently motivated by spite - he began plotting treachery after the promotion course he won a place on was scrapped due to cuts. When he met two MI5 officers posing as Russian spies, Devenney was apparently uninterested in the offer of money in exchange for information.
Devenney admitted gathering details of "crypto material" - programmes used to encrypt secret information - which could be useful to an enemy.
He was charged with collecting information for a purpose prejudicial to the safety or interests of the State between November 18 2011 and March 7 2012.
The submariner admitted a charge of misconduct in a public office in relation to meeting two people whom he thought were from the Russian secret service and discussing information relating to the movement of nuclear submarines.
He denied a second count of communicating information to another person and this will not be pursued by prosecutors.