The film had its world premiere on 20 April 1961 at the Leicester Square Theatre in London's West End and went on general release in late May on Rank's second string National circuit.
Sir Ernest Pease (James Robertson Justice), a brilliant but acerbic scientist, is the subject of a television program based on This Is Your Life during which he is re-united with past acquaintances. A flashback ensues.
In 1942, Pease is working on very important aircraft research during the Second World War. He needs to take a trip on a bomber to gain first-hand knowledge of the environment under which his special equipment is to be used. However, no one must know who he is. He goes as Lieutenant Farrow, a Royal Navy public relations officer. The bomber is hit over Germany and, ignoring a crewman's warning, Pease is sucked out through a hole in the side of the aeroplane, but parachutes safely to the ground.
He is captured and sent to a prisoner of war camp mostly occupied by Royal Air Force officers. His excellent command of German causes him to be suspected of being a spy, but when his real identity becomes known to Group Captain Travers (Norman Bird), the senior British officer, he informs the men in his hut of his importance and that his escape is a top priority. Among Pease's roommates are Jimmy Cooper (Leslie Phillips), "Jock" Everett (Stanley Baxter), and "Bonzo" Baines (Jeremy Lloyd).
Pease is offered an opportunity to escape through a tunnel with two other men. However, he expects the pair to be easily recaptured (which does in fact occur). He instead plans to go into hiding after the escape attempt. When the Germans eventually assume he has succeeded in getting away and lose interest, he will walk out of the camp, disguised as one of three visiting Swiss Red Cross observers, along with Cooper and Baines. Crucial to the plan is that Everett looks like the camp Lager (compound) officer, Major Stampfel (also played by Baxter, even though he describes him as "hideously ugly"). He must impersonate Stampfel, as he will be escorting the delegation. The escape committee, headed by Wing Commander Piggott (John Le Mesurier), are very dissatisfied with Pease's plan, but Pease is determined to see it through. The plan nearly comes unstuck at the last moment, when another prisoner, "Grassy" Green (John Forrest), is revealed as an astute undercover Luftwaffe intelligence officer. He takes them at gunpoint, but mistakes Everett for Stampfel and is "dealt with". Pease, Cooper and Baines walk out of the camp and eventually make their way back home.
Returning to the television programme, Pease is reunited with Baines, now a leading designer of ladies' foundation garments; Cooper, a missionary in India; Everett, a West London undertaker; and Stampfel, who has become a popular entertainment manager at a British holiday camp.
The escape plan, to walk out of the camp dressed as Red Cross observers, was used in real life. It was briefly mentioned in Paul Brickhill's book The Great Escape.
There were in fact two such 'Swiss Commission' escapes from German POW camps holding RAF prisoners - Oflag IXA/H, Spangenberg, in 1941, and Oflag VIB, Warburg, in 1942. The escape in 'Very Important Person' is based upon the latter, which was an Army-RAF joint effort, and not the one mentioned by Paul Brickhill. Both escapes are described by Charles Rollings in his books 'Wire and Walls' and 'Wire and Worse'.
The film's screenplay was later made into a novelisation with the same title by John Foley, which has erroneously caused John Foley to sometimes be credited as author of the novel, which the film is based upon. However, it was the other way around: his novel is based on the film.