Although its plot is taken from the history of ancient Rome, 'Caligula' is not made in the style of sword-and-sandal epics like 'Spartacus' or 'Gladiator'. (That style of movie-making was out of favour in the late seventies). Rather, it more closely resembles a cross between a soft-core porn movie and a video nasty. At least, the shortened 150 minute version does. I have never seen the full 210 minute version, but to judge from the descriptions of it on this page, it would seem closer to a cross between a hard-core porn movie and a video nasty.
As one would expect from a film produced by the publisher of 'Penthouse', there is much naked flesh to be seen, and the film lovingly catalogues Caligula's sexual perversions, including his incestuous affair with his sister Drusilla. What is perhaps unexpected from the publisher of a magazine so closely associated with the heterosexual male lifestyle is that there is as much male flesh as female on display and distinctly homoerotic overtones to many scenes. The obsession with sex is balanced by an equal obsession with violence, as though Bob Guccione, Gore Vidal and Tinto Brass were trying to kill two taboos with one stone. (It is a remarkable coincidence that the director of such a brazen film should be called 'Brass' and the scriptwriter of such a gory one should be called 'Gore'). Characters are put to death or mutilated in a variety of sadistic ways, and there is a charming scene of homosexual rape.
The Emperor Caligula and his predecessor Tiberius were certainly known for their debauched lifestyles, so the film's concentration on sex and violence is not necessarily historically inaccurate. I do, however, question whether such a concentration is necessary to help us understand this period in Roman history. Both 'The Fall of the Roman Empire' and 'Gladiator' were set during the reign of Commodus, an Emperor quite as cruel and licentious as Caligula. In neither case did the filmmakers find it necessary to turn their film into a mixture of 'Up Pompeii!', 'Emmanuelle' and 'The Texas Chainsaw Massacre', and both those films are artistically far better than 'Caligula'.
The acting in the film is not particularly bad, with a few exceptions such as the horribly wooden Teresa Ann Savoy as Drusilla. Malcolm McDowell makes a suitably insane Caligula. (Suitable, that is, in the context of this film. The real Caligula was doubtless both cruel and eccentric, but historians have debated whether he was actually mentally ill). The great mystery is exactly why so many distinguished British actors should have agreed to take part in such a trashy production. In the case of Helen Mirren (the only Dame of the British Empire with a past as a porn star) it was probably connected to her rather regrettable tendency to alternate between the highbrow and the sleazy, but heaven alone knows what Peter O'Toole and John Gielgud thought they were doing. Unlike some other famous stage actors, such as Laurence Olivier and Richard Burton, Gielgud did not always look completely at home in the cinema, but here he gives a dignified interpretation of the role of Nerva, a decent and honourable Senator of the old school. Unfortunately, in the context of this film any attempt at dignity is as out of place as a pearl on a dunghill.
Guccione clearly succeeded in his ambition for this film to become something of a cult classic of decadence. (Whether Brass and Vidal had quite the same ambition for the film is open to question). The film does not, however, succeed upon any other level, either as art cinema or as a study of the politics of dictatorship. Even seen as erotica it is second-rate. 4/10