'Brisk' was a British unrealised plan, developed from 'Alloy' and to be implemented in the event of any German seizure of the Iberian peninsula, to take the Azores islands group, part of Portugal, in order to provide air and naval bases for the closing of the 'Atlantic gap' in which U-boats could operate with little threat of British air attack (December 1940/1941).

The concept was revived in the spring of 1943 as 'Lifebelt'.