In 37 AD, Caligula (McDowell) is the heir to his syphilis-addled grandfather Tiberius (O'Toole), who leads the Roman Empire in a life of sadistic hedonism. And as emperor, Caligula takes this to new heights of depravity. While frolicking with his adored sister Drusilla (Savoy) and slutty wife Caesonia (Mirren), he consolidates his power by getting rid of competition like his cousin Gemmellus (Brive), the prefect Macro (Badessi) and his mistress Ennia (Asti). But paranoia still sets in.

Opening with the biblical quote, "What shall it profit a man if he should gain the whole world and lose his own soul," what follows is a deluge of megalomaniac debauchery. And while there's clearly an effort to depict the reality of Roman decadence, the film's stagey sets, camp performances and a cast of Penthouse-style centrefolds make it impossible to take seriously. Not to mention venerable hams like Gielgud and O'Toole, even if they, McDowell and Mirren are actually rather good.

Most notorious is the rampant nudity, violence and sex, which becomes ludicrously gratuitous because of leering direction that attempts Fellini-esque gusto but is constantly subverted by orgiastic excess. What's amazing is that it hangs together at all with such badly botched filmmaking. There are no actual credits for writing, directing or editing; it claims to be adapted from Gore's "original screenplay", Brass is credited with "principal photography" (with "additional scenes" by Guccione and Lui), and editing is by "the production".

In the end, the narrative is truncated to allow for maximum explicit degeneracy, so the film isn't much more than a series of shocking scenes that exploit history in an attempt to boost Guccione's magazine sales. In many ways, it's like there are two unrelated casts and crews: one making a historical drama and the other a hardcore porn. But it's pacey and kitsch enough to keep us watching. And usually chuckling at the sheer audacity of it all.

As an American property developer (Landau) checks out one of his investment in the Docklands, including a visit with his favourite rent boy (Drysdale), the nearby Empire State club is a hub of activity. A journalist (Cranitch) is investigating rumours of drug deaths, a young kid (Hoganson) is trying to find a missing friend, a lovelorn drunk (Foreman) wants to liberate his hostess girlfriend (Hickling), and the big boss (McAnally) demands his money back from a young upstart (Sears). It's all going to crash down around a naive woman (Harrison) who's in over her head.

The film really captures the energy of the period, when massive super-clubs attracted a startlingly broad crowd. Despite being essentially a gay venue, the vast Empire State features a range of sexualities and ages, with virtually everyone on easily accessible designer drugs. Meanwhile behind the scenes, local crime bosses are pulling the strings, making a lot of money by stirring in other money-making ventures like boxing leagues and prostitution.

All of this is portrayed in a pure 80s style, with low-budget filmmaking that's often rather cheesy due to the lurid colours and pulsing music. Not to mention the big hair, appalling fashion and sweaty gym workouts. But all of this vividly depicts this boom time, when derelict warehouses were turned into trendy neighbourhoods and shiny new business districts. Meanwhile, the TV is full of reports on violent demonstrations against Thatcher. And after the brief, teasing prologue, we know this story will end in carnage.

There are so many characters in this film that it's not always easy to figure out the interconnections between them, but it's intriguing to see the events unfold from so many points of view. Most (but not all!) of the actors are very good. There isn't a central plotline, although Harrison has the closest thing to the focal role. And it's great to see Landau in here, offering some wonderfully smooth menace.

In a futuristic city where workers toil underground, the privileged class lives in modern splendour, enjoying its Son's Club and Eternal Gardens. But when Freder (Frohlich), son of the city's master Joh (Abel), goes underground in search of the beautiful Maria (Helm), he discovers the dark truth firsthand. Back home, he challenges his father to create a more just system, then he teams up with a dismissed factory manager (Loos) to help launch a rebellion. Meanwhile, Joh and his mad inventor (Klein-Rogge) have a counter-revolutionary plan of their own.

Lang's filmmaking is still impressive today, with its stunning views of the futuristic city combined with a gripping story that's grounded in emotion and a soulful yearning for justice. The film's design is simply magnificent, with dazzling sets, big effects and a cast of thousands. But the narrative and characters are just as memorable, combining political intrigue with gritty thrills as Freder is shadowed by his father's creepy, thin goon (Rasp) and as Maria is cloned as a robotic rabble-rouser.

The image most people remember is the iconic female robot, clearly a prototype for Star Wars' C-3PO half a century years later. And her connection to each man gives the film an emotionally potent kick as it drives the increasingly harrowing events that follow. Add to this the messianic overtones surrounding Freder, and the plot clamps down on us with romance, action and dark drama, never letting go for a second as it builds to an apocalyptic climax.

This reconstructed version contains 25 minutes of footage that were thought to have been lost forever. Discovered in Buenos Aires in 2008, these timeworn scenes have been lovingly re-inserted exactly as in Lang's original version of the film, adding much more resonance to the already timeless story. Classic movies don't get much more essential than this one.

At the Marcia Blaine School for Girls in 1932 Edinburgh, Miss Brodie (Smith) is the glamorous star teacher. For her, it's all about teaching her 14-year-old students to live properly and avoid anything that might appear vulgar. Goodness, truth and beauty come first, while she urges the girls to look for their prime and live it to the full. Of course, this florid romanticism isn't exactly part of the curriculum. And her reality is somewhat different, as she flirts with a seductive, married artist (Stephens) and a more suitable colleague (Jackson).

Smith is simply divine in this Oscar-winning role, with her cut-glass accent and hilariously proper lectures. She seems almost as shocked at the repercussions of her rather promiscuous life as her students are when they find out. It's an arch, often hilariously over-the-top character, and Smith gives her a real soul underneath her stiff posture and idealistic views. She also draws on her energy and force of will to make the character both a little terrifying and darkly sympathetic, especially in the chilling final act.

Her interaction with both Stephens and Jackson bristles with possibility, as the men fill very different roles in her life and in her affections. They're thoroughly effective performances, counter-punched by Johnson's tough headmistress. And the girls add surprising layers of texture, most notably Franklin as the tough-minded one who charges into difficult lessons and Carr as the earnest new student who finds herself in scary new situations.

As the plot develops and expands, all of the characters find additional depth that overcomes the early stereotypes. Meanwhile, the plot continues forward into intensely provocative territory; it may be set in a more prudish era but it feels pertinent in today's politically correct culture. In this sense, Jean's defiant refusal to buckle even when she knows she might be wrong is truly inspirational. And Smith makes it entertaining even when things turn serious.