1961: the days of happy motoring and AA patrolmen were duty-bound to salute to every passing passenger that bore an AA badge on their vehicle, and hapless patrolman Harry Thorpe struggles with his job. He frequently clashes with his superior, one Inspector Leonard Spanwick, who also happens to reside in a caravan in Harry's back garden and is romantically involved with his blowsy sister Joyce. Leonard often makes Harry's life difficult, and he struggles to keep his local branch afloat and recruit new members, which is compounded by the intense competition from the rival RAC organisation, who are keen to drain away their trade. Although he's dedicated, Harry often has difficulty trying to stay up to date with some of the organisation's recent advancements.
Mrs Bannerman, who normally does the AA laundry, holds out for higher wages. Leonard's unwillingness to pay forces the men to walking around in unwashed uniforms. Leonard organises a first aid exercise, with embarrassing results. Joyce opens a roadside café, and thinks Leonard is proposing to her again, but he's only trying to persuade her to do the laundry.
Spurned by Joyce, Leonard is hitting the bottle. His carelessness results in an injury to Harry's foot, making him unable to go out on the road. It's Bank Holiday, so Leonard goes out on patrol while Harry looks after the office. After becoming bored with filing and inventories, Harry pretends to be Leonard while answering the phone. He gives Headquarters the impression that his men are ""on the verge of mutiny"". They are alarmed and send someone to investigate. Harry has to continue the pretence of being Leonard. Meanwhile the real Leonard Spanwick is having problems with a Maserati — and its owner. Leonard later has to ""carry the can"" for Harry's dealings with Headquarters. He gets his revenge by locking Harry in a cupboard and making him miss his date with Catherine.
Joyce is taking an interest in Raymond Cartwright, from the RAC. Leonard is enraged when he finds out. Harry is toying with the idea of a transfer from the AA to the RAC. Joyce offers to ""put in a word"" with Raymond for him. Harry takes Catherine out for a meal. Leonard invites himself along. When Joyce and Raymond turn up in the same restaurant, Leonard causes a 'scene'. Raymond tries to talk Harry into compiling a 'dossier' on Spanwick to prove that he's really committed to the RAC. Leonard tries his hand at being an 'agony uncle' on the radio. Joyce falls out with Raymond Cartwright when he tries to 'forbid' her wearing slacks. Leonard has a 'take away' delivered by the Indian restaurant and gets more than he bargained for.
Catherine wants to go on a hotel inspectors' course but Leonard won't recommend her. He thinks she's 'getting ideas above her station'. Meanwhile, Leonard receives post from his twin brother, Maurice, who says that he's planning to visit. Because the letter is several weeks late, he's due to arrive later that same day. Leonard has claimed that he's engaged to a beautiful young woman named Catherine. He offers to recommend Catherine for the hotel inspectors' course if she will help him to maintain the deception while his brother is in town. When Maurice arrives, he bumps into Joyce at her café and takes a fancy to her.
Leonard has been invited to give a talk on 'The Motorist and the Law' to the Women's Institute. He expects the AA men to attend, but they all claim to have prior engagements, as many of them are in fact doing a bit of moonlighting for extra cash. Harry, for example, runs a fresh fish delivery service and Bannerman sells his wife's homemade preserves.
It's the time of the Cuban Missile Crisis and everyone is worrying about the possibility of nuclear war. Harry is planning a weekend away with Catherine. He's worried that any 'hostilities' will interfere with his plans. Leonard gives the AA men a talk on surviving a nuclear attack. He suggests that each of the men should protect himself by turning up his collar and putting a brown paper bag over his head. Leonard misunderstands a phone call and becomes convinced that a nuclear war has started. He tells Harry to take Catherine down into the cellar while he goes to get Joyce. She's preparing a meal when Leonard bursts in and carries her off to the old air-raid shelter in the garden. The house blows up because Joyce had not had chance to light the gas in the oven. Leonard spends the night with Joyce, while Harry and Catherine sleep together in the cellar. Next morning, Joyce is angry with Leonard when she discovers that there has not, in fact, been a nuclear attack.
