A night fighter can be best defined as a fighter aircraft that - either by design or by adaptation - could fly at night or when other aircraft were grounded due to poor visibility. To be able to fulfil its role, a typical night fighter would be a twin-engined aircraft with the nose section crammed full of electronic equipment, typically radar, direction finders to find the airbase at night, a variety of communications equipment plus special lighting inside the cockpit.

The early night fighters were conversions of either heavy fighters or light bombers. The Bristol Beaufighter was an early example and the de Havilland Mosquito came later on. A few types were later designed from the start for the role of night fighters, as in the P-61 Black Widow.

The Luftwaffe also experimented with single-engine planes in this role, which they referred to as Wilde Sau (wild boar). In this case the fighters, typically Focke-Wulf Fw-190s, were equipped only with a direction finder and landing lights. Lacking radar they were not that efficient in their role.

One of the main functions of night fighters was to act as Pathfinders. Entire squadrons of Mosquitos were assigned this task. Pathfinders flew ahead of the heavy bombers such as Lancasters and Flying Fortresses at low altitudes (this in the dark of night) located the targets and dropped flares and small incendiary bombs over the designated targets. These would light up the sky for miles around and were readily visible to the bombers flying at high altitude.

The de Havilland Mosquito was a twin-engined aircraft of plywood monocoque construction, designed originally as a fast, unarmed light bomber. This concept was regarded as an aberration by the authorities, but the performance of the Mosquito silenced the critics. At night it operated pretty much with impunity over Germany to the end of the war, because the Luftwaffe never had a night fighter fast enough to intercept it.

The Mosquito also served with distinction as fighter-bomber and reconnaissance aircraft. It was one of the finest aircraft of WWII, with versatility only matched by the German Junkers Ju 88. The night fighter versions remained in production until 1947. The amazingly adaptable design was effective for day and night fighting, day and night bombing, anti-shipping attack, and photo reconnaissance. The bomber version of the Mosquito could deliver the same bomb-load to distant targets as the four-engined Boeing B-17.

Mosquitos were also used as high-speed transports by British Overseas Airways Corporation (BOAC) to maintain communication with neutral Sweden and bring back strategic items such as ball-bearings. Passengers, if any, rode in the bomb bay. Because of the glued-and-screwed wooden construction, early Mosquitoes were not suited to the tropics where exposure to high humidity and rain caused the airframe to warp and the glue to dissolve.

The Mosquito Nightfighter with a crew of two was powered by two Rolls-Royce Merlin XXI engines. With a wing span of 54ft and a length of 50ft, it was capable of a maximum speed of 380mph with a ceiling 36,090 ft (11,000m). Armed with four 20mm cannon, or four 7.7mm machine guns, it also had a rack for two long range fuel tanks, or two 500 lb bombs or eight rockets. The Mosquito also carried out some famous operations, like the attack on the Gestapo head quarters in The Hague. In that raid a 5 story building was leveled by 3 "waves" of 2 aircraft, using incendiaries and high explosives, and destroying all records the Gestapo had collected over the years on resistance fighters and their families, and hiding addresses of Dutch Jews. Another famous attack was the break out of more than 250 prisoners in the prison of Amiens, France. The first bombers destroyed the guard houses, and following aircraft breached the walls to enable the men inside to break free. This remarkable feat was put in progress because the French Resistance had mentioned the planned execution of numerous resistance fighters

It was fast, and it was small: the recipe for a hard target. The Mosquito bomber saw the lowest loss rate of all Allied bombers. It astounded the brass in its maiden flights (it was faster than the Spitfire Mark of the time by 20mph) and kept the enemy very busy indeed. For the enemy to get a Mosquito down in a dogfight they had to get lucky. They couldn't catch it in level flight and they couldn't climb higher.

The Mosquito Nightfighter had excellent performance, excellent handling, excellent armament; it may have been as good an all round aircraft that flew in WWII.

Michael Russell Your Independent guide to Aviation