A secret Cold War nuclear bunker which was considered the 'first defence against the Russians' and could accommodate 400 politicians underground will open to the public. The historic bunker in Barnton Quarry, near Edinburgh, was built in the 1950s in the midst of fear of Soviet power - and remained a secret until the 1980s. Deep underground in Corstorphine Hill, four miles from the capital, it served as Sector Operations Centre for co-coordinating RAF fighter jets and protected Scotland from attack by Russian long-range nuclear bombers until around 1960. It was used as a control centre where information was analysed, and became a base for a radar air defence system.