CNN's Richard Quest said Cameron's attempt to go after tax cheats could be seen as good populist politics and an easy shot as he tries to distract from other matters.
James Cameron, the director of "Avatar, " and Richard Branson, with Virgin Oceanic, are each planning to head for the deepest seas of the western Pacific with single-person subs that travel hundreds of feet a minute.
Mr Cameron also confirmed that former head of the Army General Sir Richard Dannatt would become a Tory defence adviser and may serve in a future Tory government.