The Jokers (1967)

Michael Tremayne (Michael Crawford) and David Tremayne (Oliver Reed) are always trying to find some way to succeed with cleverness rather than simple drudgery. Michael is constantly living in his brother's shadow as the one who gets caught. After Michael is forced to resign from the Army after an episode of unappreciated cleverness, the two decide that their careers would go better with a large amount of publicity, so they decide to steal the Crown Jewels from the Tower of London. Bombs, misdirection, disguises, and acting allow them to enter the tower with all of the alarms turned off.