An embittered Army interpreter serving in Afghanistan betrayed Britain to become an agent for Iran, a court has heard.
Tehran-born Daniel James was a "Walter Mitty"-style fantasist who believed he had been passed over for promotion and been the victim of racism, a jury was told.
James was in a "unique position" working for General David Richards, who was commander of international forces in Afghanistan, the Old Bailey heard.
He sent coded messages to an Iranian military attache in Kabul and told him "I am at your service", it is alleged.
Mark Dennis QC, prosecuting, told a jury: "During the latter part of 2006, the defendant's loyalty to this country wavered and his loyalties turned to Iran, the country of his birth.
"He turned his back on those with whom he was serving in Afghanistan and sought to become an agent for a foreign power."
The defendant was seeking to provide information to insurgents fighting coalition forces and others "who may yet become involved or who may directly or indirectly support the insurgent elements", Mr Dennis said.
James, 45, of Cliff Road, Brighton, denies communicating information useful to an enemy and a second count of collecting such information on a USB memory stick, both charges under the Official Secrets Act. He also denies wilful misconduct in public office.
Mr Justice Roderick Evans told jurors that parts of the trial would be heard in secret and that they would have access to documents marked "Nato Confidential", which they would have to treat confidentially.
It is expected to last three to four weeks.
