Leigh Light

It was a powerful (22 million candelas) carbon arc searchlight of 24 inches (610 mm) diameter fitted to a number of the British Royal Air Force's Coastal Command patrol bombers to help them spot surfaced German U-boats at night.

Efforts to reduce this minimum were not successful, so wing commander Humphrey de Verd Leigh hit upon the idea of using a searchlight that would be switched on just when the target was about to disappear on radar.

Introduced in June 1942, it was so successful that for a time German submarines were forced to switch to charging their batteries during the daytime, when they could at least see aircraft approaching.

Wing Commander Humphrey de Verd Leigh, an RAF personnel officer, devised a solution after chatting with returning aircrew.

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.

[8] A Swordfish III was also fitted with a Leigh Light under the starboard wing, at some point, although it is unclear where the battery pack was stowed as the ASV radar scanner apparently filled the torpedo area.