IRAN is to keep secret global positioning and communications equipment captured when its Revolutionary Guard took 15 British sailors and marines hostage last month.

Military sources say the three rigid inflatable boats used by the boarding party from HMS Cornwall carried portable computer units for the Xeres network, a system that allows the mother ship to track them with pinpoint accuracy from up to 15 miles away. It also allows the detachment on the boats to pass back instant digital intelligence and to navigate using satellite guidance.

A source told the Herald: "Even the Americans are envious of the Xeres system. It's top-of-the-range electronic kit and regarded as mission essential' by UK naval forces in the Gulf.

"We've no doubt Tehran is busy reverse-engineering it to find out how it works and how it can be copied. On past performance, the Iranians will also keep the three sea boats and the crew's personal weapons."

Iran kept three Royal Navy boats seized in the Shatt al Arab waterway near Basra in June 2004, when eight naval personnel were held and subjected to mock executions before being released five days later. The latest ho