Bomben ab
("bombs away")
The Depot under attack? The Luftwaffe & Unternehmen Nordwest (the German Invasion of England)
The construction of the Depot's 62 air raid and blast shelters was essential as Grantham hosted armamant factories. Aveling-Barford produced 47 Bren carriers per month. The British Manufacture and Research Company (BMARC), a 60-acre site employing 7,800 workers manufactured 20mm Hispano Suiza aircraft cannon and explosive bullets for the Oerklion anti-aircraft gun (100,000 weapons and 56 million rounds of ammunition). Known to the Germans as the Hispano Suiza Cannon Factory, precise details of one January 1941 attack are known. Additionally, there were several satellite factories including one half a kilometer from the Depot, and two more just north of Belton Park. Another major Grantham factory was Ruston & Hornsby Ltd that produced the Matilda mark II (A12) tank under the leadership of the Vulcan Foundry Ltd of Warrington, Lancashire. Starting from 3 September 1939, Grantham had a total of 386 air raid alerts during the war (figures 1 & 2).
A 1,000lb bomb landed in Grantham Railway's marshaling yard. Lt. John Ernest Gilkes tried to defuse a bomb fitted with two detonators, each equipped with a booby trap device. Three minutes later a terrific explosion killed Gilkes instantly.
Figure 1: a WWII 500lb German UXB found in London in 2017 explodes.
Figure 2: example of a 550lb WWII bomb exploding in Munich
Figure 3: Grantham air raids
The Luftwaffe attacked Grantham 21 times with 88 alerts between 6th September 1940 to 26th October 1942 (figure 3). The last attack targetted St Vincent's Hall, HQ of No. 5 Bomber Command just 2 km away from the Depot. Altogether, eighty-eight persons were killed and 149 injured; damage occurred to numerous houses (Harlaxton Manor Archives). The Grantham casualty rate of 4.4 per 1,000 of the population fell just behind the rates for Coventry, Plymouth and Liverpool (figures 6 & 7). In the end, only two of the air raids hit BMARC and one bomb fell on Ruston & Hornsby Ltd.
Figure 4: Knickebein transmitters (black dots) and how they guided Kuftwaffe bombers to Derby.
The main risk to the Depot came not from deliberate Luftwaffe attack so much as from British electronic warfare countermeasures used against the Luftwaffe's Knickebein (‘Bent Leg’) navigational bombing aid beam (Havers & Sheppard 2013).
One pair of Knickebein transmitterswas set up at Stollberg Hill in Nordfriesland and at Kleve (Cleves) near the Dutch border (where Anne of Cleves came from. Figure 4). They were found to cross above the Derby Rolls Royce factory, which manufactured Merlin engines for Spitfires with the beams passing close to Grantham.
Electronic countermeasures successfully altered the drop target where the beams crossed. This led to large random bomb drops in open countryside, such as 10 High Explosive bombs and 30 incendiaries dropped on Barkston 3 km from the Depot. The actor Arthur Lowe, Captain Mainwaring of Dad's Army was based at Barkston RAOC depot and tasked with servicing searchlights in the vicinity. The Depot also benefited from Grantham's 1942 'QF' decoy sites (see below).
Figure 5: a relatively intact heavy anti-aircraft battery emplacement 60 meters in diameter half a mile to the south east of the Depot (Google earth 2010). It was armed with two 3-inch guns and GL Mark IA radar in 1942, when it was manned by 244 Battery of the 78th Royal Artillery Regiment. It appears similar to this more detailed photograph near Barnsley (photographed on 10 August 2012 (NMR 28324_002). List Entry 1019872. © Historic England Archive: Photographer - Dave Macleod).
Regarding ground attack, Grantham was a nodal point or Anti-Tank island - defensive points centred on major road junctions, bridges or natural features (Osborne 2004, 20th Century Defences in Britain: The East Midlands). Designed to delay the advance of German forces, giving time for Allied reinforcements to move to the area.
Military infrastructure for the defence of Grantham and its RAF airfields still remain in situ (figure 5). Despite this defence only one Junkers 88 was shot down over Grantham , along with 3 Messerschmidts and possibly one other enemy aircraft brought down by ramming by an Airspeed Oxford at nearby Barrowby.
Activity over Grantham was reduced by Q- and K-sites night-time and daytime decoy airfields respectively, operating at Folkingham, Allington & Boothby Pagnall that lured enemy aircraft away. As an example, the design of the latter site was ARMY BOMBING DECOY A35, STARFISH BOMBING DECOY SF80A, or CIVIL BOMBING DECOY C63A. It was constructed, 4 miles south of the Depot, the typical distance from a protection target. The 'QF' decoy consisted of a series of controlled fires lit during an air raid to replicate a target struck by bombs.
The 'QL' decoy featured a grid of lights set out to resemble a military or urban area during a poor blackout. In November 1942 a 'Temporary Starfish' decoy was commissioned for the site to protect the town of Grantham. This was effectively a larger scale 'QF' decoy, which was designed to simulate an urban area struck by bombs. The site continued in use until 1943.
Figure 6: an air-raid shelter was hit by a bomb in Stuart Street, Grantham in 1942. Thirty-people were killed, and 500 left homeless. See Oral History relating to this incidence.
Figure 7: the same view of Stuart Street today.
Figure 8: German invasion map of the Grantham area. (Nord Midlands. England Blatt Nr. 6. Militargeographische Objektkarten. Oberkommando der Wehrmacht 1941)
Unternehmen Nordwest
At the beginning of December 1939 the German army began planning for an invasion of England (figure 8). On 6 December 1939, General Franz Halder, Chief of the General Staff, demanded maps of England. By the 13th of December, the Army gave a draft plan to the Kriegsmarine and the Luftwaffe, for their views on a landings in East Anglia from the German Bight (the North Sea adjacent to the Kiel Canal). The plan was described as Studie or Unternehmen Nordwest. It had envisaged an assault along the coastline between the Wash and the River Thames (original documents in German). By the end of December 1939, the plan was side-lined because of the difficulties of air support and the strength of the Royal Navy,
Parts of Nordwest were integrated into Unternehmen Seelöwe, 'Operation Sealion' - the main 1940 German invasion plan for Britain. Hitler called off Operation Sealion indefinitely from 17 September 1940, because of the failure to destroy the RAF, who would have decimated any invading troops. It is unlikely that MI5 knew the details of either plan until post-war. Nevertheless, regional towns laid plans for any possible invasion as late as 1942. Locally, these envisaged an enemy landing in the Wash, sweeping inland along the A52 from Boston. See Bingham's Operation Bugbear. The role of the RAF Regiment in these plans is unclear. Local ground crews had responsibility to defend airfields, although the Regiment were to provide anti-aircraft units. It is unlikely the the Regiment would have remained static to defend the Depot. The local Home Guard had responsibility for resisting the German invasion with secret arms caches located at Manthorpe, Barkston, Culverthorpe, Welby and Londonthorpe.
Figure 9: Wehrmacht geology map 1941
The German army had a large number of military geologists who examined coastal morphology, water supply, construction materials and cross-country trafficability for the German invasion force. Grantham was on their list (figure 9).