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D2 Heavy Anti-Aircraft Battery - a brief history

Image showing the Command Post at D2 shortly after the acquisition in 2017
The Command Post at D2 shortly after the acquisition in 2017 | © National Trust Images/John Miller

Situated between Dover and St Margaret’s and close to the two cross-channel gun emplacements ‘Jane’ and ‘Clem’, the D2 Heavy Anti-Aircraft Battery was in use throughout the Second World War. Now part of our Wanstone Rediscovered project, we’ll look back at the history of D2 and explore its features that can still be seen today.

Early History

On Christmas Eve 1914, shortly after the outbreak of the First World War, Dover was hit by the first aerial bomb ever to fall on British soil. The importance of its port, together with its vulnerable location had already been recognised and led to it having some anti-aircraft defences at an early stage. Over time these developed into an early form of integrated air defence, with guns and interceptor aircraft backed up by searchlights and ‘listening stations’ to provide early warning of aircraft or airships from the sound of their engines. At nearby Fan Bay, a 15 ft (4.6 m) diameter concrete sound mirror was used to detect aircraft from autumn 1917: this can still be seen.

The first indication of the site of D2 being considered for an anti-aircraft battery came in the late 1920s with plans to protect Dover Harbour with one battery of 3-inch (76 mm) calibre guns near here and one at what became D1, on the hill at Farthingloe, west of Dover.

The start of the Second World War

When the 223rd (Cinque Ports) Heavy Anti-Aircraft Battery were called up for the start of the Second World War, they did so with four of the new 3.7-inch (94 mm) calibre guns. Dover Harbour was a vital port in the early weeks of the war – especially as a base for minelaying in the Channel. As a result, a further four 3.7-inch guns were brought here at outset of the war until the end of 1939 – but with no apparent increase in the 140 or so men available to operate them.

Sandbags and dugouts

The original D2 guns were mobile units that could be towed and temporarily housed in gun pits made of sandbags – filled with earth and lumps of chalk dug from the ground on which they stood. Command posts controlling the firing of the guns were in dugouts excavated into the chalk. Both were unsuitable for long term use: the dugouts flooded in wet winter weather, rain leached the chalk out through the sandbag fabric, and paths eroded leaving white chalk to clearly show the position of D2 from the air.

Black and white image showing Second World War Vickers mobile anti aircraft gun with crew just before the outbreak of war in August 1939
3.7-inch Vickers anti-aircraft gun with crew of the 223rd (Cinque Ports) Heavy Anti-Aircraft Battery just before the outbreak of war in 1939. By kind permission of Trevor Wiltshire. Mr Wiltshire's father ('Gunner WWD Wiltshire') served at D2 and is third from the right, partly hidden. | © National Trust/Trevor Wiltshire

The permanent D2

In 1940, permanent concrete gun pits and associated roads and buildings were constructed for four guns on the present site. To make D2 harder to spot from the air, roads and roofs were darkened by covering them in black tar or asphalt. Camouflage paint and netting were used to break up the outlines of guns, buildings and emplacements.

On the morning of 14 June 1940, the mobile guns in the sandbag gun pits were replaced with static guns in the concrete structures - the changeover took just 2 hours. The timing was helpful, coming only 10 days after the end of the Dunkirk evacuation and just as activity at D2 started to ramp up with the Battle of Britain.

Detailed records of the actions at D2 show that in the 109 days from 9 August to 25 November 1940, D2 fired a total of 4,970 3.7-inch shells in 307 individual actions against enemy aircraft: an average of approximately 46 rounds per day.

Image of decommissioned 3.7-inch anti-aircraft gun at Mudchutes, East London, similar to those installed at D2, near Dover.
Decommissioned 3.7-inch anti-aircraft gun at Mudchutes, East London. Note the similarity of the lockers and mounting pads to those visible at D2 | © Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license - author - Leutha

The D2 guns

In the middle of each concrete gun pit was a Vickers Armstrong 3.7-inch quick firing (QF) gun mounted on stout steel legs and semi-permanently bolted down: many of these bolts can still be seen.

Each gun could fire a 28 lb (12.7 kg) high explosive shell to a maximum altitude of 36,000 ft (10,973 m). A good gun crew might fire perhaps 10-12 aimed rounds per minute, although this was roughly doubled later in the war, when powered aiming and mechanised fuze-setting simplified the tasks of the gun crews.

The gun pits

All four of the gun pits at D2 had similar layouts. Each gun pit was octagonal in shape and about 40 ft (12 m) across. Two opposite sides had metal gates, while the other six sides had concrete ‘recesses’ (or cupboards). The gun pits were numbered 1 to 4 in an anticlockwise direction, with gun 1 on the right when facing the enemy. The - now faint - labelling for gun pits 1 and 2 can still be seen.

Image showing one of the D2 gun emplacements. The six lockers are distributed around the central gun mounting and held the shells and essential spares for the guns.
Image showing one of the D2 gun emplacements. The six lockers are distributed around the central gun mounting and held the shells and essential spares for the guns. | © National Trust/Gordon Wise

The recesses

The six recesses were lettered from ‘A’ to ‘F’ in a clockwise direction, starting from the left when entering from the command post. Recesses ‘B’ and ‘E’ (the middle ones on each side) were different from the other four, providing greater protection for their contents. Recess ‘B’ was the store for the ‘limber gunner’. The limber gunner would traditionally maintain the gun and would open and shut the breech during firing. Recess B therefore held spare parts, lubricants, and tools, together with related documentation for the gun.

Recess ‘E’ held anti-gas equipment, specifically the gas capes to protect the 10-12 men that were usually to be found in each gun pit. Gas drills were regularly carried out, although poison gas was never used in the Second World War.

The other four recesses held ammunition. Each recess normally held 40 rounds on racks and the position of the recesses meant that whichever direction the gun was firing, an open door to an ammunition recess would always be nearby.

The magazines

There were two magazines, one between emplacements 1 and 2, the other between emplacements 3 and 4. Both magazines were of a similar design, but the magazine between emplacements 1 and 2 had a lower roof. Inside the magazines some markings can still be seen where the batches of ammunition were recorded. Each magazine would have been expected to hold 560 rounds. Each gun pit would hold another 160 rounds in the concrete recesses, so that the entire gun site would be expected to hold some 1,760 rounds.

Image showing the entrance to the western (No.1) magazine at D2. The roofs of these low concrete buildings were painted black for camouflage and protected by reinforced concrete walls with gun ports. The remains of the black camouflage paint can be seen on the edge of the roof.
The entrance to the western (No.1) magazine at D2. The walls and roofs of these low concrete buildings were camouflaged and protected by reinforced concrete walls with gun ports. The remains of the camouflage can still be seen on the edge of the roof and in some of the green coloration of the walls. | © National Trust / Robert Hall


Most of the shells would be high explosive. At the pointed top of each shell was a fuze that could be rotated to set the time on a clockwork mechanism. The time would run from when the gun was fired to when the shell exploded – this could be as long as 43 seconds.

In summer 1944, the proximity fuze was introduced. This was triggered by the change in the nearby electromagnetic field caused by an object such as an aircraft, and and removed the need to estimate the time of flight of the shell and set the fuze.

Image showing wartime writing on the walls of a magazine recording the batch numbers of the shells stored there
Wartime writing on the walls of a magazine recording the batch numbers of the shells stored there | © National Trust / Robert Hall

The command post

The command post was the nerve centre of D2 and appears to have been constructed in two main phases. The first phase was the concrete part of the building (on the west side) together with the concrete walls that created roofless ‘rooms’ on the north side that came into use in June 1940. The later brick building extension on the eastern side accommodated the increasing amount of electrical radar and plotting equipment that was being introduced.

Radar and Optical Sighting

Although D2 had gun-laying (‘GL’) radar from early 1940 – it was initially only useful for giving warning of approaching aircraft. Early radar sets gave accurate estimates of range but were unable to give sufficient information on height and direction. As a result, anti-aircraft guns were aimed using optical instruments and the eyes of the gunners. This meant that gunfire at night or in cloudy or foggy conditions was inaccurate and usually ineffectual.

Optical sightings, range data from radar and information from a heightfinder – a rather large and cumbersome piece of optical equipment – were fed into a predictor, a kind of analogue computer. An operator would track the aircraft through a viewer using control wheels. Levers and dials on the sides allowed input of the altitude and other factors. The predictor gave an output that was sent electrically to each of the guns, giving the elevation and direction they should point at, together with the fuze setting needed for the estimated time of flight of the shell.

Image showing the command post at D2 with the aircraft aiming instrument mounting pads in the foreground.
D2 Command post with the triangular heightfinder mounting in the foreground and predictor mounting on the low concrete block directly outside the black doors on the low concrete building | © National Trust/Gordon Wise

Radar takes over

By the second half of 1944, radar had advanced sufficiently that anti-aircraft guns could be aimed and fired solely using radar data, regardless of daylight and weather conditions.

The Chain Home radar station at Swingate provided early warning of aircraft attack, while the gun-laying radar at D2 had a much shorter range, typically around 15 miles or 24 km. The information from Swingate and other sources was passed to the filter room at the HQ of Fighter Command at Bentley Priory, Stanmore. Coordination between AA Command, the RAF and other services was vital to avoid friendly aircraft coming under fire.

Radar operators were in short supply as healthy men were posted from AA Command to the field forces for service overseas. Elsewhere, the solution often lay in the women of the Auxiliary Territorial Service (‘ATS’) filling many of these technical roles, but the frontline position of Dover prevented them from being used at D2. However, Canadian radar operators were used at D2 and later in the war, Polish troops were used to man some of the Dover guns.

Image showing the D2 gun store after clearance of the overgrowth.
The "gun store" building at D2 was converted into an improvised pillbox in February 1941 by cutting embrasures for guns into its walls, as can be seen in this photograph. In the distance are two radar transmission towers at Swingate. The left hand one is original and dates from around the start of the Second World War and is often stated to be the oldest surviving radar transmission tower in its original location. | © National Trust/Robert Hall

The end of the war

The last piloted aircraft ever to be shot down by AA Command over Britain crashed into woodland near Barham between Dover and Canterbury on 23 August 1944. Nevertheless, work proceeded to modernise D2 with short wave radar, electronic predictors and powered guns that did not need to be aimed by hand-cranking.

With the emergence of the first jet-powered reconnaissance aircraft, it was apparent that future aircraft would be flying at higher speeds and at greater altitudes, beyond the limit of the existing anti-aircraft guns. A new D2, equipped with more powerful 5.25-inch (133 mm) guns was constructed at what is now Sherley’s Farm. Progress on building this new site was slow and continued beyond the end of the war in Europe into at least late 1945.

Post War

The 3.7-inch D2 site remained in occupation until at least the end of 1945, but on an increasingly ‘care and maintenance’ basis. Later, the guns were removed and placed into storage with other equipment. Although not permanently staffed, the site was maintained, and a high wire security fence was constructed around the core of the gun site. The rusting remains of the fence posts remain around the site today - some are visible in the foreground of the photograph above.

Technological developments of jet interceptor aircraft and guided surface-to-air missiles led to the disbanding of AA Command in the mid-1950s and D2, which by then had been renamed DV2, fell into disuse and was abandoned.

The site was returned to agricultural use, with the emplacements, buildings and roads largely intact in the late 1950s, but the cost of demolition was prohibitive, and the site was left to return to nature. During the 1990s a concrete road that connected the accommodation huts to the D2 site was lifted to allow more economic use of the land.

The 3.7-inch D2 site was acquired by the National Trust in 2017. In 2019 a project to conserve and preserve D2 for future generations was drawn-up and in 2022 a National Lottery Heritage Fund grant of £199,000, along with substantial local donations enabled work to start, conserving the site and its buildings.


We would like to thank White Cliffs' volunteer Robert Hall for his extensive research into D2's history and for his generous contributions to this article.

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Image showing the Command Post at D2 shortly after the acquisition in 2017


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