A secret Second World War command bunker buried four metres deep in the White Cliffs of Dover opens to the public on Friday 13 November 2026, after lying hidden beneath a Kent field for decades.

The Fan Bay plotting room was ordered by Winston Churchill and housed the first land-based computer-aided targeting system. It acted as the brain for a gun battery used to defend Dover and attack German ships in the Channel, according to Jon Stewart, who led the excavation for the National Trust.

From Friday, the public can visit the concrete-encased room on National Trust guided tours, entering through a hatch in a field, putting on a hard hat and head torch and descending 18 steps down the main access shaft, as the soldiers who worked there did more than 80 years ago.

A computer built to outgun the enemy

The plotting room held a 1.8-metre-long electromechanical computer known as a fire direction table. Target data was relayed from the Fortress Command at South Foreland and processed into precise direction and elevation settings for the three Fan Bay six-inch guns, allowing crews to calculate the position of moving ships and send firing instructions to the gun crews.

The battery can be traced directly to Churchill. Soon after his fight them on the beaches speech, he visited the Kent coast and was alarmed to see enemy ships passing through the Strait of Dover unchallenged, while Dover faced regular bombardment from German guns in occupied France. In a memo in July 1940, he wrote that Britain had to fight for command of the straits by artillery, ordered the most advanced technology to be used and demanded weekly updates. The guns were ready within 100 days, and the plotting room was completed 64 days later. The guns were known locally as Churchill's pets.

Rediscovered after 60 years underground

The plotting room was secretly mothballed in 1957 and remained classified until 1981 because of its military importance. Its computer was deliberately destroyed in 1957 to stop it falling into enemy hands. The entrances lay completely hidden beneath more than a metre of soil until volunteers rediscovered the room in late 2017.

Stewart was the first person to enter the bunker when it was rediscovered. He described it as a Tutankhamun moment for a conflict archaeologist: the team had researched the people who served there, then suddenly found themselves standing in their office.

The room has been preserved much as the team found it, rather than recreated. Remnants include old newspapers on the floor, old shoes and official notices still stencilled on the walls. Chalked graffiti in one service tunnel reads heroes fan hole Dodds and Petitt, probably the men who hauled heavy cable through the tunnels during construction.

The people who worked in the plotting room

Up to 10 people at a time worked in the plotting room, but only a handful of the operators are known by name. They include Wallas Eaton, an actor who later appeared in the television comedy Up Pompeii, and Lance Bombardier W. P. Bryant, a tailor who Stewart suggested probably had a head for numbers.

What is known about the machine comes from a manual and ghost markings on the floor, and Stewart is keen to hear from anyone whose family members served at Fan Bay, because the records are scant. He compared the find to the rescue of Bletchley Park in the 1990s, calling it a new hidden history, and stressed that the system was not a map with markers being pushed around, as in war films, but a cutting-edge electromechanical computer.

Visiting the Fan Bay plotting room

Tours run from the White Cliffs of Dover, with tickets at 10 pounds per person and a six-pound charge for non-member car parking. Visitors face a 900-metre walk from the car park, and the site is not suitable for people with restricted mobility, as the only entrance is the steep 18-step staircase. Children must be aged eight or over and able to climb it unaided.

The Trust says the plotting room joins its historic sites around the White Cliffs, alongside Fan Bay Deep Shelter, Wanstone Battery and South Foreland Lighthouse.

Frequently asked questions

What is the Fan Bay plotting room? It is a Second World War command bunker buried in the White Cliffs of Dover. It housed an electromechanical computer that aimed the three Fan Bay six-inch guns at German ships in the Channel.

When does it open to the public? Guided tours begin on Friday 13 November 2026, run by the National Trust from the White Cliffs of Dover. Tickets cost 10 pounds per person.

Why was the bunker secret for so long? It was mothballed in 1957, its computer destroyed, and it stayed classified until 1981. National Trust volunteers only rediscovered it in 2017.