A rediscovered Second World War plotting room hidden under the white cliffs of Dover is set to open to visitors for the first time, the National Trust has revealed.

Built in 1940, the Fan Bay Plotting Room was a war operation centre which helped direct guns defending the Strait of Dover as Britain’s front line following the fall of France.

Hidden beneath its guns and deep in the cliffs, the plotting room was home to some of the most advanced military technology of its time, such as the fire direction table, to calculate firing data and co-ordinate artillery operations.

It came as part of a national priority to strengthen Britain’s coastal defences during the war, where Dover became known as part of Hellfire Corner as it endured shelling attacks from occupied France just 21 miles away.

After the war, the secret site was abandoned and buried under soil in the 1970s.

It was rediscovered in 2017 and became the focus of National Trust research and conservation, and is now ready to open to visitors from Friday.

National Trust’s Jon Barker said: “There’s something very special about standing in a place that has changed so little since the people who worked here left.

“Rather than recreate the past, we’ve carefully conserved the plotting room so visitors can experience it much as we found it, with all the marks of its history still visible.

“It’s a rare opportunity to discover a completely different side of the white cliffs, and a fitting tribute to everyone who has helped bring this remarkable place back into public view.”

The underground space as it was found includes its peeling paint, wartime graffiti and pipes and ducts on display.

Alongside preserving the physical site, volunteers have unearthed the personal stories of those who served at Fan Bay, which volunteer Gordon Wise said has “changed how I see the room”.

The White Cliffs of Dover volunteer said: “A name in a service record, or a detail in a photograph, helps connect the surviving marks on the walls with someone’s working day.

“There are still questions to answer, but each discovery helps us build a clearer picture of the people behind the machinery.”

Tours of the plotting room must be booked in advance through the National Trust.