At the end of the First World War, Britainís anti-aircraft defences, which had been built up from virtually nothing during the past four years, were dismantled and once more almost ceased to exist. It wasnít until the mid-1930ís that, with the re-arming of Germany, Britain began to look at its own armament position. The standard heavy anti-aircraft weapon, indeed the countryís entire heavy ack-ack stock, was the 3-inch gun, rapidly becoming obsolete against modern enemy aircraft. The 3.7 inch gun, which was to replace the 3-inch, had just been developed but was not due to go into production until 1937; the defence requirement of light, quick-firing guns, against low-flying attack, had hardly been considered.
Even then, there was no more than pedestrian action and for two more years committees and reports came and went. It was not until 1937 that the situation changed and, almost overnight, home defence policy changed from one extreme to the other. Top priority was to be given to the manufacture of 3.7-inch guns. In its early version this highly sophisticated weapon could reach up to a practical ceiling of 23,000 feet and fire at 25 rounds per minute. Alongside the higher-firing 4.5-inch gun, which being already in existence as a naval artillery piece provided a convenient partner, the 3.7-inch was soon to become the backbone of the ack-ack defences during the Second World War.
Meanwhile, against low-flying aircraft, the now-legendary 40mm Bofors gun was not only imported in quantities from Sweden but was also to be built under licence in Britain. With an effective ceiling of 5,000 feet the Bofors could track an enemy plane and pump out rounds at a rate of 120 per minute.
Construction of the specially designed reinforced concrete emplacements to hold the 3.7-inch and 4.5-inch guns began in 1938. These followed a number of standard patterns which developed throughout the war, but generally they were octagonal or square, about 40 feet across and comprised an open concreted enclosure with shoulder-high external walls. Around the inside there were ammunition alcoves where the shells would be stored on wooden racking. In the centre, the steel framework of the hold-fast, for anchoring the gun, was embedded in the concrete of the base. The emplacements were grouped in fours or eights, half batteries or full batteries. The difficulties of getting a shell anywhere near the target, and then to explode just as it arrived, had long been appreciated and to give the battery the best chance of success, fire from the group was directed from a central command post where instruments for determining the height, range, speed and direction were located and transmitted electrically to the gun positions.
By the outbreak of war many of these sites were complete, although a shortage of weapons meant that some remained empty until the deficiency could be made up. However, much of the ground lost had been recovered and 3.7ís, 4.5ís and some of the older 3-inch, which were still with us, waited in their emplacements...
During the course of the next five-and-a-half years, A.A. Command grew out of all recognition. At the height of the command over a quarter of a million men were engaged and heavy anti-aircraft guns occupied a thousand sites throughout Britain. Each site had grown to the size of a small army camp with around 30 huts providing accommodation, kitchens, stores and all the necessities of a permanent encampment. However, it was the formation of mixed batteries in the summer of 1941 which had one of the major impacts on ack-ack development. The idea had been first mooted by General Pile, later to become Commander-in-Chief of A.A. Command, in 1938. This was a controversial proposal and at first there was a great deal of opposition to enlisting women to fight the enemy directly. However, many were enthusiastic, not the least Churchill who, in a brilliant outflanking move, volunteered his daughter to join a mixed battery. It is one of the memorable aspects of World War Two ack-ack defence that mixed batteries were an unqualified success. Within 18 months, 170,000 ATS were engaged at heavy 3.7 and 4.5-inch gun sites.
"Necessity is the mother of invention". This was never proved to be more true than during the wartime years. The technology of anti-aircraft gunnery, and its success rate, had more than kept pace with the performance of enemy aircraft. The invention of radar and in particular its application to ack-ack gunnery revolutionised the ability to predict the path of an enemy bomber and to place shells in its path. The faithful 3.7-inch gun developed and improved through a number of variations and wasnít finally phased out, astonishingly, until the end of the anti-aircraft gun era in 1959. During the latter part of the war, with enemy aircraft flying ever higher, an even more powerful weapon was introduced, the 5.25-inch gun. Like the 4.5-inch, this was a naval-designed gun. With a rate of fire of ten rounds per minute it could launch a shell weighing three-quarters-of-a-hundred-weight up to eight miles into the air.
From June 1944 the threat of German bombers was replaced by a totally new aerial weapon - the VI flying bomb. Launched both from "ski ramps" in northern Europe and from bombers over the North Sea, this "revenge weapon" immediately became the primary target for the ack-ack gunners. However, the sites carefully chosen for anti-aircraft defence, largely around centres of heavy population, were hardly suitable for attacking the new threat which was going to explode wherever it was brought down. So, in a massive relocation exercise thousands of guns, both heavy and light, were uprooted from the sites which had become their permanent homes and re-emplaced in dense "gun belts" along the south and east coast. These ĎDiverí sites themselves became permanent fixtures over the winter of 1944/45 with all the necessary accommodation and command facilities of the previous sites. Over 1,000 ĎDiverí sites were established during the final year of war with the last V1 being brought down on 29 March 1945 off Orfordness.
Although ack-ack guns formed by far the greater part of the anti-aircraft ground defences, there was a lesser-known weapon which was deployed at many sites throughout Britain - the anti-aircraft rocket. Rockets had been used in warfare by the British as long ago as the Napoleonic Wars and trials as anti-aircraft devices had been carried out early in 1939. By the end of the following year the design of the rockets, looking something like a six-foot drain pipe with a warhead at one end and four fins at the other, had improved to the point that production could begin and by the latter part of 1941 nearly 2,000 projectors, as their launch cradles were officially known, were available. On site, it was usual for these projectors to be deployed in multiple ranks and as many types could hold more than one rocket it would be possible to launch over 100 missiles into the sky at one time to explode in a great cloudburst of steel shrapnel.
The Essex Picture
There were around 40 permanent heavy anti-aircraft gun sites within the present boundaries of Essex. These included the full range of 3.7, 4.5 and 5.25-inch gun emplacements together with a number of rocket sites. Wartime records show, not surprisingly, that the sites were mainly grouped in the south of the county on the direct route from Germany to London, with specific concentrations around Chelmsford and Colchester. Gun location lists, produced during the war, are a fund of information on the whereabouts of the sites, what was in them and who manned them. However, information on some sites remains elusive with virtually nothing yet having been discovered on one or two.
For example, "TN7: Furtherwick", on Canvey Island, is well documented. In April 1940 there were four 3.7-inch mobile guns manned by 59 Regiment, 167 Battery. By May 1942, 2 Regiment, 11 Battery manned the site with four 4.5-inch guns equipped with GL Mk II radar. In December the following year, 184 Mixed Regiment, 625 Battery had taken over. In January 1946 everyone had gone. However, in complete contrast, why is there no record of the four-gun site at Bradwell Wick which shows so clearly on 1945 aerial photographs? Where exactly was the ack-ack site at "C1: East Mersea"? Getting back to Furtherwick, it used to be in open fields but now the whole area is built over and has been for years. Sandwiched between the houses is a sports and play area and buried underneath some strange big grassy mounds are... the gun emplacements.
At "H5: Little Oakley" the best part of four square emplacements still remain, together with their ammunition chambers and some of the heavy wooden racking which supported the shells. At "TN10: Vange", many of the original brick and concrete huts have survived as farm buildings and, like Canvey Island, there are more of those big grassy mounds... However, it is at "ZE7 Lippitts Hill", south of Waltham Abbey, that it all comes together.
Owned by the Metropolitan Police as a training establishment since 1960, it is a startling survival of 1940ís and post-war military architecture. Two of the original 3.7-inch gun emplacements remain, together with the command post and the magazine bunker. Late in the war the site became a prisoner-of-war camp and many of the wooden huts built first to accommodate the gunners, then the P.O.W.ís and latterly the police trainees, still stand in fine condition. One of the most unexpected features of the site is just inside the main gate - a full size statue of a man, carved out of a solid block of concrete by prisoner-of-war 540177 Rudi Weber. Among the first of such sites to be statutorily protected, "Furtherwick", "Little Oakley" and "Lippitts Hill" are now designated Scheduled Monuments.
Walking around Central Park, in Chelmsford, it is hard to imagine that from 1943 to 1944 the park played host to 64 twin rocket projectors manned by 211(101 Essex Home Guard) "Z" AA Battery R.A. The site was known as "C12 Recreation Ground". The rocket projectors were located on the open ground between the river, the lake, Park Road and the then cattle market with the radar cabins on the other side of the river in the cricket ground. Each projector, which could launch rockets up to an altitude of 19,000 feet, was manned by two men. The battery went into action many times against German bombers attacking Chelmsford. During one raid, by some 30 aircraft on the night of 13 May 1943, there were fires all over the town. Bombs dropped on the houses in Park Avenue; the Territorial Drill Hall, in Market Road - with its stored ammunition - was set alight by incendiary bombs; and a dozen Eastern National buses at their depot in New Writtle Street were ablaze. The rocket siteís radar cabins were hit and put out of action, but the battery continued to fire under visual control. Two Home Guardsmen of the battery received recognition for their courageous actions that night.
The last manning at "C12 Recreation Ground" was on 11 September 1944.
© Fred Nash, ECC