was fired into the air from a buoy previously dropped by the plane. The surfaced submarine could then be seen in silhouette as the plane approached. Wing Commander Humphrey de Verd Leigh, an RAF personnel officer, devised a solution after chatting with returning aircrew. This was to mount a searchlight under the aircraft, pointed forward and allowing the submarine to be spotted as soon as the light was turned on. He then developed the Leigh Light on his own, in secret and without official sanction—even the Air Ministry were unaware of its development until shown the completed prototype. At first it was difficult to fit on aircraft due to its size. Leigh persisted in his efforts to test the idea, and garnered the support of the Commander-in-Chief of Coastal Command, Sir Frederick Bowhill. In March 1941 a Vickers Wellington DWI that conveniently already had the necessary generator on board (it had been used for anti-magnetic mining operations using a large electromagnet) was modified with a retractable "dustbin" holding the lamp and proved the concept sound. At this point the Air Ministry decided that the idea was worthwhile, but that they should instead use the Turbinlite, a less effective system which had been originally developed as an aid for night-time bomber interception. After trials they too eventually decided to use Leigh's system, but it was not until mid-1942 that aircraft started being modified to carry it. Development assistance and production was by Savage and Parsons Ltd. of Watford led by Jack Savage. Operation Two types of Leigh Light entered operational use: The Turret type, fitted on Wellington aircraft, was a searchlight mounted in a retractable under-turret controlled by hydraulic motor and ram. The maximum beam intensity was 50 million candelas without the spreading lens and about 20 million candelas with the lens. Total weight was . The Nacelle type, fitted on Catalinas and Liberators, was a searchlight mounted in a nacelle in diameter slung from the bomb lugs on the wing. The controls were electric and the maximum beam intensity was 90 million candelas without the spreading lens and about 17 million with the lens. Total weight was . By June 1942, aircraft equipped with ASV radar and the Leigh Light were operating over the Bay of Biscay intercepting U-boats moving to and from their home ports on the coast of France. The first submarine to be successfully sighted was the