This Kate Middleton bikini photo leaves no doubt whether she's "fit" to be royal.

Great Britain's future Princess of Wales has slipped on something white before, according to this bikini look, far sexier than the covered-up one she's expected to wear when she weds Prince William.

Professional Kate-watchers attribute Middleton's six-pack to regular workouts at the Clarence House sports club in London and beauty treatments at Richard Ward Hair and Metrospa in London's tony Sloane Square.