Steven Hayden, 30, from Purbrook, Hampshire, was paid £10,000 by the paper for a story about an alleged plot by Iraq's leader Saddam Hussein to launch anthrax attacks in the UK.

He pleaded guilty to disclosing security or intelligence information contrary to section one of the Official Secrets Act 1989.

The court was told that Hayden, who worked in a unit providing intelligence for navy ships at sea, had needed the money because of horrendous financial problems.

Details not revealed

Because of the national security implications, the details of the offence cannot be reported.

The Sun's front page for 24 March

However it is known that the document disclosed related to a potential threat by Iraq to smuggle deadly anthrax into the UK disguised as harmless liquids.

The story appeared in The Sun on 24 March 1998 under the headline 'Saddam's Anthrax in Our Duty Frees'.

London's chief full-time magistrate Graham Parkinson decided to send Hayden to the Old Bailey for sentencing because the maxiumum sentence of six months he could impose was not sufficient for such a serious crime.

The maximum sentence at the Old Bailey judge's disposal was two years.