NEWLY released documents show that a major security lapse involving anti-nuclear protesters managing to board one of the Royal Navy’s Polaris submarines sparked a furious reaction in Whitehall.

Then prime minister Margaret Thatcher was apoplectic with rage after she was informed that three demonstrators had accessed the control room of nuclear-armed HMS Repulse while it was moored at the Clyde submarine base at Faslane.

The files, released by the National Archives today, reveal that the incident led to a major review of security at the base, with sentries being given the order to shoot any intruders.

On October 10 1988, the Ministry of Defence contacted No 10 to say that three men had forced their way on to Repulse in the early hours of the morning after cutting through the Faslane perimeter fence.

A female protester was also picked up near HMS Resolution, another nuclear-armed sub.

The PM demanded an immediate inquiry. “I am utterly horrified,” she scrawled in a handwritten note.

“Examples of slackness in sensitive matters keep coming to light. I must have an urgent report. We could have been put in grave danger.”