*No spoilers* Came across film by chance - appears difficult to obtain. From memory: Three stalwarts in the shape of Rod Taylor (straight from the Australian outback), Christopher Plummer (Burton's window) and Lilli Palmer (Operation Crossbow?) head the cast in this jolly jape around the nicer parts of London in the 60's. Plot surrounds Christopher Plummer and the efforts to protect him and his high powered government position by the capable Rod Taylor. Minimal "love interest" tosh, very much in the style of a "boy's own - hit him with your left" film. Fun for all the family - buy it.
P.S. Make sure English and not German soundtrack.