I don't know what it is about David Niven but you can't root against the guy, He could play Judas and he would still play it with such charm that you wouldn't believe that he was the bad guy. That's the David Niven you get in the Pink Panther, though the other stand out in the film is the legendary Peter Sellers.
The film is about a jewel thief called The Phantom who Insp. Jacques Clouseau (Sellers) has been chasing for the better part of a decade. He sees his chance to catch him by keeping close to Princess Dala (Claudia Cardinale) who is the holder of the famous Pink Panther diamond. The Phantom is there in the person of Sir Charles Lytton (Niven) who is prepared to steal the diamond from the princess through his suave demeanor and charm.
On the surface the Pink Panther feels like one of those '50's and '60's pseudo sex romps that promises a roll in the hay but never produces. Those films were like the cushioned soft core porn of the Leave It To beaver generation. Two people in the same bed!?!?! Shame! The Pink Panther rises above that from the performances of Niven, Sellers, Cardinale, Capucine (as Mrs. Clouseau), and a young Robert Wagner as the newphew of Sir Lytton. It's actually a funny film with Seller's stealing the show one bit after another. It's not as much of a time capsule as some of the other films of its era have become. A classic that started a twenty year franchise.