'Blanket' was a small-scale British exercise by Major H. G. Hasler’s Royal Marines Boom Patrol Detachment on the Swale river, between the Isle of Sheppey and the coast of mainland Kent, in preparation for the 'Frankton' canoe-borne operation up the Gironde river estuary to attack German shipping in Bordeaux on the south-west coast of German-occupied France (10 October 1942).