In 1944 the village of Shaftesbury is evacuated as part of a German crackdown on partisan activity in the area. Pauline, an apolitical Irish nurse, is accidentally left behind with several of her friends, all of whom are killed in a Resistance ambush. On reaching London Pauline finds nursing jobs are controlled by the paramilitary Immediate Action Organization, which she is reluctant to join. She changes her mind after witnessing the Organization efficiently putting down a brawl in which an IAO officer is brutally assaulted. Pauline has no interest in fascist ideals, but thinks resistance to the occupation is only making things worse and Britain should get back on its feet. Unfortunately she discovers that separating herself from the more reprehensible actions of fascism is not so easy in practice.
The concept of the film was first developed in 1956 by eighteen year-old Kevin Brownlow, and was eight years in the making — the longest ever production schedule to date according to the Guinness World Records. It had a cast of hundreds; all volunteers with only two professional actors among them. While trying to find WW2 uniforms for the film Brownlow met sixteen-year old history buff Andrew Mollo, and the two decided to work together on the project. Brownlow would later become a prominent film historian and Mollo a leading military historian. It Happened Here also launched the career of cinematographer Peter Suschitzky, who went on to such films as The Rocky Horror Picture Show and The Empire Strikes Back.
It Happened Here contains the following tropes:
- Alternate History Nazi Victory: An opening narration explains that Britain was invaded in July 1940, with a nascent Resistance quickly crushed without outside support. The film is set four years later — the United States has entered the war and is supporting a resurgent partisan movement with carrier-based aircraft. Most German troops have been shifted to the Russian front to combat a Soviet breakthrough in the Urals, leaving the occupation of Britain to a token force, including volunteers from the British Legion of SS.
- As Himself: Colin Jordan and other British fascists played members of the IAO.
- British Nazis: For once justified. There are even actual British Nazis!
- Les Collaborateurs: The film subverts the popular view that only self-serving opportunists and power-hungry fanatics would work with an invading force.
- Day of the Jackboot: Nazis take over England.
- He Who Fights MonstersDr. Fletcher: "The appalling thing about fascism is that you've got to use fascist methods to get rid of it. We've all got a bit of it in us, and it doesn't take a lot to bring it to the surface."
- Literary Allusion Title: It Can't Happen Here, a 1935 novel by Sinclair Lewis about a totalitarian government taking over the United States.
- Moral Myopia: A female IAO Commandant reprimands Pauline for not showing "loyalty to the English people" (e.g. failing to denounce her friends). Also the IAO Political Leader at a funeral for a Black Shirt:"This rabble, this Jewish pirate scum, HAVE MURDERED OUR COMRADE!"
- Even more appalling when you realize that Colin Jordan, the man playing him, was a real British fascist.
- Newscaster Cameo: Veteran wartime BBC radio announcers Alvar Lidell and John Snagge gave their services free to voice reconstructed newsreels and radio broadcasts.
- Propaganda Machine: A newsreel gives a revisionist history of British/German relations, ending with British and German soldiers having a snowball fight on the Russian front.
- Rare Vehicles: Actual vehicles, uniforms and weapons from the era were used, all donated by various collectors.
- Reassigned to Antarctica: Pauline is demoted and sent to the countryside, a move she initially welcomes as the country hospital has none of the fascist paramilitary trappings of the ambulance corps. She then discovers the hospital is being used to euthanize foreign slave workers who have contracted TB. Also seen when a 'friend' tries to denounce Pauline for secretly trying to get some morphine. Fortunately her superior has just received a phone call announcing his reassignment to somewhere unpleasant (presumably the Russian front) and throws her out of his office.
- Released to Elsewhere: What's supposed to be a countryside hospital for workers afflicted with tuberculosis is actually in the business of euthanizing them.
- La Résistance: Subverted. The British civilians in Shaftesbury are clearly more afraid of the partisans than they are of their German occupiers.
- Retraux: Hand-held cameras, grainy footage and quick cuts were used for the newsreel, with no stock footage whatsoever being used.
- The Reveal: When Pauline learns the unpleasant truth about her new hospital.
- The Revolution Will Not Be Civilized: At the beginning of the movie, the SS are shown massacring civilians found in a restricted area. At the end of the movie the Resistance gun down unarmed prisoners from the British Legion of SS.
- Shout-Out: The movie's title is a reference to the book It Can't Happen Here, a novel deconstructing the notion that Nazi-style fascism can't take root in Western democracies by showing just how a takeover could happen.
- Shown Their Work: On one occasion a group of Bundeswehr tank officers training in Britain were surprised to see German WW2 era soldiers marching through Parliament Square; they inspected the troops and pronounced them "absolutely correct". There also actually were British SS members. Although the exact name in the film (British Legion of SS) is false, the real Legion of St. George, later British Free Corps, actually existed. However, it never reached more than fifty people overall. Their instigator, British fascist John Amery, was hanged for high treason.
- State Sec: The Immediate Action Organization, which is an entirely British group belonging to the SS.
- Training Montage: Used to show not only Pauline being taught new skills by the IAO, but also how she is being indoctrinated. At the beginning the nurses flinch when firing a Webley revolver; by the end of the montage all of them are shown coldly blazing away at their targets.
- Talking Heads: Pauline's co-workers justifying their involvement in the euthanasia program.
- The Un-Reveal: The final scene is of Pauline treating the Allied wounded after her capture, while the distant rattle of machine-gun fire is heard as the SS prisoners are massacred. We never discover her fate.
- Villains Out Shopping: A montage shows German soldiers playing tourist in London, mixing with the locals and chatting up girls.