Army and RAF Regiment versions . This example mounts a Stiffkey Sight, and displays the additional armor protecting the gunners The
British Army had first examined the weapon in 1937, when it received a number of Polish-built examples for testing. They were known as the "QF 40 mm Mark I" (QF standing for
"quick firing"). With a minor change to the
flash hider, they were designated "Mark I/2". A production licence was acquired, and the gun was converted from
metric to
imperial measurements. Numerous changes were made to the design so that it was more suitable for mass production, because the original Bofors design was intended to be hand-assembled. Many parts were labelled "file to fit on assembly", requiring many man-hours of work to complete. Testing showed that there was a serious problem with aiming the gun at high-speed aircraft. Although it could be trained quickly, aiming accurately while doing so proved difficult. In order to deal with that, the British introduced a complex
mechanical analogue computer, the
Kerrison Director, which drove the laying electrically. A three-man team operated the director by pointing it at the target whilst dialing in estimates for speed, range, and various atmospheric conditions. The director then aimed the gun using powered mounts, while a gunner loaded the clips. That eliminated the need for the lead-correcting reflector sights, which were replaced with a backup system consisting of a simple ring-and-post sight, known as a "pancake". In that form, the "QF 40 mm Mark III" (Mk II was a designation used for
a version of the naval "pom-pom" anti-aircraft gun), became the army's standard light anti-aircraft (AA) weapon, operating alongside their
3-inch 20 cwt and
3.7-inch heavy AA guns. British production started slowly and, by September 1939 only 233 equipments had been produced. However, by the end of the war, the total production of British, Canadian and Australian factories numbered over 19,000. The peak production year was 1942, when British factories produced 5,025 and Canadian factories produced 1,311. In combat, it was found that the Kerrison was difficult to set up in many situations, as well as making
logistics more complex, due to the need to keep its electrical generator supplied with fuel. In most engagements, only the pancake sights were used, without any form of correction, making the British versions less capable than those used by other forces. Eventually, an anti-aircraft gunnery school on the range at
Stiffkey on the
Norfolk coast, delivered a workable solution, a trapeze-like arrangement that moved the pancake sights to offer lead correction, operated by a new crew-member standing behind the left-hand layer. The "Stiffkey Sight" was sent out to units in 1943, arriving in Canadian units in the midst of the
Battle of the Aleutian Islands. A final wartime change to the elevation mechanism resulted in the "QF 40 mm Mark XII". A much lighter, two-wheeled carriage was also developed for
airborne use. The army experimented with various
self-propelled anti-aircraft guns based on various
tank chassis. Changes to the breech for that role created the "QF 40 mm Mark VI", which was used on the
Crusader tank to produce the
Crusader III AA Mark I. The main self-propelled version of the Bofors was the gun mounted on a chassis derived from the
Morris C8 "Quad" artillery tractor, which was known as the "Carrier, 30 cwt, SP, 4×4, 40 mm AA (Bofors)" or Morris-Commercial C9/B. Such guns were used in support of army divisions, to provide swift protection against air attack without the need to unlimber. They saw service in north-west Europe, where six SP Bofors of 92nd (Loyals) Light Anti-Aircraft Regiment, Royal Artillery, landed with the
British 3rd Infantry Division on
Sword Beach on D-Day, to protect the vital bridges over the
Caen Canal and the
Orne River (
Pegasus Bridge and
Horsa Bridge), shooting down 17 German planes. Later in the campaign, SP Bofors were used extensively for ground shoots as well as in an anti-aircraft role. In British Army service, the Bofors found a highly specialised role: during the
North Africa campaign, at the
Second Battle of El Alamein, they were used to fire
tracer horizontally to mark safe paths for units through the German minefields. That practice was further developed during operations in north-west Europe, where bursts of colour-coded tracer were used to define the axis of advance of different formations in large-scale night attacks. The
RAF Regiment was formed in February 1942, in response to the German capture of airfields with airborne troops in the
Battle of Crete, which resulted in strategic defeat on the island by numerically inferior German forces. The formation of a dedicated airfield defence force included low-level air defence, in which the Bofors L60 — the same design as the Army version — was the principal weapon for the RAF Regiment's Light Anti-Aircraft squadrons in North Africa, Malta, Italy, the Balkans, the UK (including the allocation of fifty-two squadrons to
Operation Diver defence against V-1 flying bombs in southern England), and north-western Europe (from
Normandy landings through to the cessation of hostilities). No 2875 Squadron RAF Regiment, employing the L60, became the first unit to shoot down a jet aircraft, a
Messerschmitt Me 262, with ground-based anti-aircraft fire, at
Helmond in the Netherlands on 28 November 1944. Although the Allied air forces had achieved air superiority by the Normandy landings,
Advanced Landing Grounds continued to be high-priority targets for the Luftwaffe when the opportunity presented, and that ensured that the RAF Regiment's L60s continued to be heavily used. For example, on New Year's Day 1945, during the
Battle of the Bulge, RAF Regiment Light Anti-Aircraft squadrons shot down 43 German aircraft and damaged 28 others during the
Operation Bodenplatte attacks on eleven RAF forward airfields. There were insufficient guns available to equip the RAF Regiment squadrons in the Far East during the war, and they had to make do mostly with
20 mm Hispano and
Oerlikon 20 mm guns. A Light Anti-Aircraft field regiment (one with each infantry division) had 54 Bofors guns. After World War II, the RAF Regiment continued to employ the L60 as its principal anti-aircraft weapon until it was replaced by the L70 gun in 1957. The guns were deployed in the UK, Germany, Cyprus, the Middle East, and the Far East.
Naval versions . In 1996, museum pieces like this cannon were pressed back into service as the main armament of the
Kingston-class minesweepers. The
Royal Navy also made extensive use of the Bofors. Its first examples were air-cooled versions quickly adapted for ships during the
withdrawal from Norway. After the
German invasion of the Netherlands in May 1940, the Dutch minelayer,
HNLMS Willem van der Zaan, gave the navy its first example of a water-cooled gun on its Hazemeyer tri-axially stabilized mounting. Locally produced examples started arriving in 1942, known as the "QF 40 mm Mark IV" with twin-mounts, or the "QF 40 mm Mark V" with single mounts. The navy ran through a variety of versions of the basic Bofors gun over the war, including the Mark VII to Mark XI. The British light anti-aircraft weapon already in use with the Royal Navy's, the
QF 2-pounder gun, also had a calibre of 40 mm, but was referred to as the QF 2-pdr. In the Royal Navy guns and mounts were designated separately. The following mountings were used: • Mark I: twin mounting based on American design and using American-built guns, not widely fitted. Fitted for remote
fire control. • Mark II: quadruple version similar to the Mark I • Mark III: a navalized version of the Army single mounting, hand worked elevation and training. • Mark IV: a tri-axially stabilized twin mounting, copied from, and usually known as, the "Hazemeyer". It had on-mounting fire control, and was usually fitted with Radar Type 282 to provide target range information. • Mark V: twin mounting, which superseded, and eventually replaced, the Mark IV, often referred to as the "utility" mounting. It was a simplified, unstabilised mounting based on the American twin mounting Mark I, and was designed for remote fire control. • Mark VI: a six-barreled weapon, feeding from large trays instead of clips, and designed for remote control from a dedicated radar-equipped director. • Mark VII: a single-barreled, hydraulically powered mounting, that superseded the Mark III and entered service in 1945. • Mark IX: Mark VII mount modified for electrical power, as the Mounting Mark IX and, in that form, saw service in the
Falklands War. The Mounting Mark V (Mark VC for Canadian built examples) for the 20 mm Oerlikon and QF 2 pounder guns was also adopted initially as an interim mount for the Bofors. It was a single-barrelled mounting with hydraulic power, and was known as the "Boffin". The final British Bofors mounting to see service was the "Stabilized Tachymetric Anti-Aircraft Gun" (STAAG), which was twin-barrelled, stabilised, and carried its own
tachymetric (i.e. predictive) fire control system, based around the centimetre Radar Type 262, capable of "locking on" to a target. The mounting was heavy (17.5 tons) and the high-vibration of the gun mounting made it a poor location for sensitive valve electronics and mechanical computers. The STAAG Mark I carried the radar dish over the gun barrels, where it was subject to damage during firing so, on the STAAG Mark II, the set was shifted to the roof of the control cabin. STAAG was ultimately too difficult to maintain in the harsh environment of a warship and was replaced by the Mounting Mark V, with the fire control equipment located remotely, then by the single Mark VII and, ultimately, with the
GWS20 Seacat missile system. The final version of STAAG was fitted to the RN
Type 12 Whitby-class anti-submarine frigates and the
Type 41 Leopard anti-aircraft and
Type 61 Salisbury air direction frigates, completed from 1956 to 1958. The cruiser
Royalist was also fitted with the STAAG Mk 2 during modernisation before transfer to the RNZN in the 1950s. Initially, it had three STAAG CIWS, the STAAG in Q position was removed in 1960, but it carried two mounts until the end of its service in
Southeast Asian waters, in 1965. In 1956 during the
Suez Crisis, the crew of
Royalist seemed to find the STAAG a reasonably effective anti-aircraft weapon in
Operation Musketeer. == U.S. versions ==