It's 1940 and Britain is on the alert for an imminent Nazi invasion. With full-time troops occupied overseas, the coastal defences are left to a handful of veteran soldiers - The Home Guard. And in Walmington-on-Sea, one inept, feeble and inadequately armed platoon is very keen to do its bit.
Starring some truly great character actors such as Arthur Lowe, John Le Mesurier, Clive Dunn and Bill Pertwee, Dad's Army was written by Jimmy Perry and David Croft, who went on to create It Ain't Half Hot Mum, You Rang M'Lord? and Hi-de-Hi! but their celebrated writing careers all began because jobbing actor Jimmy wanted a breakthrough role on TV.
Following war service and a scholarship at RADA, Jimmy Perry learnt his stagecraft in repertory theatre, eventually running his own theatre company and scoring some small parts on television. But, after seventeen years as an actor, he was hungry for a major role and dreamt up the idea for Dad's Army - based on his own experiences in the Home Guard when he was sixteen - as a way to secure himself a plum part. The role he had in mind, Private Walker, would eventually go to James Beck after Perry was advised against being both writer and star, but it was a small price to pay in the long run.
David Croft, meanwhile, was working as a BBC comedy producer and had racked up many years of experience in television production. Whilst he had worked in script editing and made writing contributions to shows, Croft didn't necessarily see himself as a TV writer, but all that was about to change when his wife Ann - a theatrical agent - introduced him to Perry, one of the actors on her books, who pitched him his sitcom idea.
The pair took Perry's brainchild to the head of BBC comedy and, whilst he liked the outline for The Fighting Tigers (as it was called) he decided to change the name to one he had come up with. And, as Perry had never written for TV before, he suggested Croft should write the scripts with him.
Dad's Army was an immediate hit with audiences and the show would regularly get 18 million viewers tuning in to watch the antics of Captain Mainwaring and his men. Running for nine years with a total of 80 episodes, the sitcom also spawned a feature film and a long-running stage show starring the TV cast.
Knew all that already? Don't panic! Here are some fascinating facts you might not know about Dad's Army.