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 terminal hypochondriac who is devastated at having been passed as fit.
The new recruits are assigned to Sergeant Grimshaw (William Hartnell). Grimshaw is 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 Nora (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 he is overheard bemoaning his lot to Copping. The squad decide 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.
- William Hartnell as Sergeant Grimshaw
- Bob Monkhouse as Charlie Sage
- Shirley Eaton as Mary
- Eric Barker as Captain Potts
- Dora Bryan as Nora
- Bill Owen as Corporal Copping
- Charles Hawtrey as Peter Golightly
- Kenneth Connor as Horace Strong
- Kenneth Williams as James Bailey
- Terence Longdon as Miles Haywood
- Hattie Jacques as Captain Clark (Medical Officer)
- Terry Scott as Sergeant O’Brien
- Cyril Chamberlin as the Gunnery Instructor
- Norman Rossington as Herbert Brown
- Frank Forsyth
- Basil Dingham
- Edward Judd
- Anthony Sagar
- Jack Smethurst
- Patrick Durkin
- James Villiers
- Henry Livings