By Thomas Harding, Defence Correspondent
At GCHQ headquarters in Cheltenham, listeners fluent in Farsi will be monitoring the mobile telephone and signalling airwaves of the Revolutionary Guards.
MI6 sources inside Iran will be giving assistance on Teheran’s thinking to help steer the diplomatic effort.
RAF Nimrods, based at Basra Air Station, Iraq, will also be circling with eavesdropping equipment.
As the intelligence-gathering resources run at full tilt, the SAS will be preparing to put in troopers.
An adviser from the regiment’s Revolutionary Warfare Wing has been moved to the Gulf to assist diplomats and MI6 agents.
But it will have become apparent that any strike against Iran will only go ahead with the approval of America.
The SAS standby squadron in Hereford, who are permanently at three hours’ notice to move, will yesterday have been waiting to hear if they are to be called in.
The soldiers, who practice hostile entry and marksmanship for several hours each day, would then be moved to a forward base in Cyprus, Qatar or elsewhere in the Gulf.