A Royal Navy submariner from Northern Ireland has admitted collecting secret coding programmes that could be useful to an enemy of the UK.
Petty officer Edward Devenney, 30, pleaded guilty at the Old Bailey to gathering details of encryption programmes in breach of the Official Secrets Act.
He also admitted a charge of misconduct in a public office in relation to a meeting with two people he thought were from the secret service of another state.
Devenney admitted meeting two people whom he thought were from the Russian secret service and discussing information relating to the movement of nuclear submarines.
He contacted a foreign embassy to try to pass to Russia "crypto material" - programmes used to encrypt secret information - and information linked to the operation of HMS Trafalgar and two nuclear submarines.
However the two people he eventually met were from British secret services.
The British Official Secrets Act charge was collecting information for a purpose prejudicial to the safety or interests of the state between 18 November last year and 7 March this year.
Devenney denied a second count of communicating information to another person and this will not be pursued by prosecutors.
He was remanded in custody for sentencing on 12 December at the Old Bailey, when parts of the hearing will be held in secret.