Electrician Bert Harris (Anthony Newley) visits Chiselhurst Caves with his girlfriend Rene (Joyce Blair) but angers petty crooks Spider (James Booth), Holy Mike (David Lodge) and Dancer (Al Mulock) because he dances with Doll (Anne Aubrey, pictured below), Spider’s curvacious Moll.
Later, Bert repairs a burglar alarm at Macey’s jeweller’s shop and allows Jinx (Bernie Winters), one of Spider’s mob, to believe he is The Cat, a notorious cracksman.
And so Spider and the gang compel Bert to join in on a raid on Macey’s.
Bert luckily secures the loot and intends to return it, but there is much rushing about and violence aboard the Jazz Boat – a Thames pleasure cruiser bound for Margate – before wily Detective Sergeant “flatfoot” Thompson (Lionel Jeffries) corners Spider, Holy Mike, Dancer and the gems, but lets Bert, Rene and Jinx (who helped Bert retrieve the stones) go free.
Ted Heath and his band are seen and heard at their best. The boat used in the film was the MV Royal Sovereign.
Bernie Winters, James Booth and Al Mulock reprised their characters of Jinx, Spider and Dancer in the 1960 film In The Nick, also directed by Ken Hughes and starring Anthony Newley and Anne Aubrey.
Det. Sgt. “Flatfoot” Thompson