The Canal Defence Light (CDL) was a British “secret weapon” of the Second World War, based upon the use of a powerful carbon-arc searchlight mounted on a tank. It was intended to be used during night-time attacks, when the light would allow enemy positions to be targeted. A secondary use of the light would be to dazzle and disorient enemy troops, making it harder for them to return fire accurately. The name Canal Defence Light was used to conceal the device’s true purpose.
The only surviving CDL-equipped Matilda tank is in the collection of the Royal Armoured Corps at The Tank Museum, Bovington, Dorset, in Britain.