SEPTEMBER 6, 2013: Visitors could get a chilling insight into the Cold War right on their doorstep.

A nuclear bunker which aimed to detect a deadly attack and warn the public was open as part of the Doors Open Days festival.

The underground monitoring post is 15 feet underground in a remote field on the outskirts of Skelmorlie and has stunning views over the Clyde.

Chief observer Frank Alexander took over the lease of the building in 2004 when it was just a shell.

(Image: Newsquest)

His interest was sparked by his work in radiation protection for energy firm EDF in the 1980s, at Hunterston B Power Station.

He fitted it out with authentic equipment in a bid to recreate the mood of an era when the nuclear threat was at its greatest.

 The volunteer, who was kitted out in the Royal Observer Corps uniform, gave the Telegraph a sneak peak of the secret facility.

As you climb deep into the depths of the earth on steel ladders you get a real sense of taking a journey into the past.

A constant blip — ‘the sound of peace’ — emanates from a device on the wall.

The noise would change to attack warning if a bomb was activated.

During our tour, Mr Alexander demonstrated the various uses of the equipment.

The main pieces of kit are the ground zero indicator, designed to identify where a nuclear explosion had taken place, and a bomb power indicator — which would have measured the pressure caused by the blast.

 The final instrument, a radiation detector, could be pushed through a special hole in the bunker into a tube outside to gauge levels of radioactive fall out.

Frank said: “The post at Skelmorlie was built in 1965 to monitor and report on the effects of a nuclear attack in the UK.

“It was one of a number of posts throughout the UK and acted as a reporting and monitoring system as part of the Civil Defence System set up by the British Government.”