Site played vital role over many decades

Edzell airfield was opened in the 1930s as a civilian facility on what had been a military site during the First World War.

The airfield returned to RAF service as RAF Edzell in 1940.

In the late 1950s it was used as a motor racing circuit.

Only a few races were held before the airfield reopened. One of the last sports car races on the circuit was won by future double World GP champion Jim Clark.

In 1960 RAF Edzell was leased to the United States Navy to house a Naval Security Group Activity during the Cold War.

The US Naval Security Group Oceanographic Monitoring Station monitored the North Sea, British coastline and European Continent, listening for radio transmissions from the Soviet Union and its allies.

RAF Edzell was part of a network of 16 high-frequency direction finder facilities around the world that monitored the electromagnetic spectrum from 2 to 32 megahertz.

Up to 3,000 personnel were said to have been stationed at RAF Edzell.

The end of the Cold War and advances in technology made the HF network obsolete, and the base closed in October 1997.

By that time, staffing levels had fallen to 300 local and 700 military personnel.

The closure marked the end of 37 years of US Navy operations and 85 years of RAF service.

The base in February 1960, when it was leased to the United States Navy.

The entrance to the base.