Never Let Go (1960)

"Peter Sellers in a new and exciting role!"

John Cummings, an unsuccessful London cosmetics salesman, has his unpaid-for car stolen by a hood in the employ of Lionel Meadows, sadistic organiser of a car conversion racket. As the vehicle is uninsured, and since the police seem indifferent, Cummings decides to find it himself — and gets himself involved in an underworld battle.