Newly married Mary Sage (Shirley Eaton) is distraught when her husband Charlie (Bob Monkhouse) receives his call-up papers during their wedding breakfast. He travels to Heathercrest National Service Depot, meeting fellow recruit Horace Strong (Kenneth Connor), a chronic hypochondriac who is devastated at having been passed as fit.




The new recruits are assigned to Sergeant Grimshaw (William Hartnell). Grimshaw will soon be retiring from the army and takes on a £50 bet with Sergeant O'Brien (Terry Scott) that his last bunch of squaddies will be his first champion platoon.




With beady-eyed inspection from Captain Potts (Eric Barker) and disgruntled support from Corporal Copping (Bill Owen), Grimshaw decides to use some psychology and treat his charges kindly rather than simply shouting at them. But basic training does not start well and he struggles to take his platoon through it. They include failure Herbert Brown (Norman Rossington), upper-class cad Miles Heywood (Terence Longdon), rock 'n' roller Andy Galloway (Gerald Campion), delicate flower Peter Golightly (Charles Hawtrey) and supercilious university graduate James Bailey (Kenneth Williams). His attempts seem doomed.




Mary is determined to spend her wedding night with her husband and smuggles herself into the depot to get a job in the NAAFI, a situation Charlie is eventually able to legitimise. Strong spends most of his time complaining to the Medical Officer, Captain Clark (Hattie Jacques). It is only the adoration of doe-eyed NAAFI girl Norah (Dora Bryan), which he initially rejects, that makes him realise his potential and inspires him to become a real soldier.




On the eve of the final tests, Grimshaw is in despair, but his squad overhears him bemoaning his lot to Copping. The squad decides to win the best platoon prize at all costs. On the day, they indeed beat the other platoons at all tasks and Grimshaw is awarded the cup for best platoon. On Grimshaw's last day, the men present him with a cigarette lighter as a retirement present and to say thank you.