Early censorship is of course now largely little more than historical hysteria from a self-appointed industry body towards apparently salacious entertainments like Damaged Goods (1919) and Human Wreckage (1923). Less so, as the author notes, was the blatant political censorship wielded to prevent filming at the front in the First War for two years, or in 1926 against Eisenstein's Battleship Potemkin, banned in the wake of the General Strike.

By the time the Second War dawned, censors had contended with both Mae West's sexual baiting, and the birth of the horror movie with Lugosi's Dracula (1931) and Karloff clomping about in the following year's Frankenstein - the former was pre-censored by some 7 minutes, the latter lost its celebrated child murder - although neither is comparable to the longest ban in British history with Todd Browning's masterful Freaks; made in 1932 and unavailable until 1963.

At the time the British Board of Film Censors (they went coy, if no less scissor-happy, in the 1980s as 'Classifiers') performed a double function - made up of the nicely middle class and ex-military, they not only slashed finished films, but pre-censored scripts before a single frame was even exposed. In the years preceding Hitler's annexing of Europe this meant two Gaumont works dealing with Nazism - A German Tragedy, City Without Jews - were rejected; script examiner Colonel Hanna did "not consider the subject a desirable one at the present juncture." And, as Mathews notes, the only reference found to black servicemen fighting for the Empire is Richard Todd calling his dog - "Nigger, Nigger" - in The Dam Busters (1955).

The book is at its best though once our torturous tale reaches the 1960s. Kitchen-sink had birthed a new realism and the result were films like Victim (1961) - with an explicitly gay Dirk Bogarde - and Richardson's Tom Jones. At the time, the Board was presided over by John Trevelyan, the first great name of censorship. Thought to be more liberal than his examiners, it did not prevent films (later recognised as classics) being outlawed - Sam Fuller's Shock Corridor in 1963, and a year later the same director's quite extraordinary child abuse parable The Naked Kiss both suffered bans. For Trevelyan's Board however such films posed a threat to censorial authority - local authorities were flexing their muscles to override the BBFC, especially in London where the Fuller films and others were granted certificates for public exhibition.

Nudity had arrived on British screens in the 1950s with a spate of naturist films like The Garden of Eden and Naked as Nature Intended, but it would be Lindsey Anderson's If... and the Swedish Hugs and Kisses (both 1968) that finally broke the mould for full-frontal sexual incitement. Unconsciously they heralded a golden age for screen provocation with the liberal censorship of the slow-motion blood-letting in Peckinpah's The Wild Bunch (1969), and the nude-wrestling of Russell's 1969 Women in Love; it was Russell who again tested the limits of free-expression a year later with his revered and reviled sex and mayhem epic The Devils. Andy Warhol's Flesh arrived on these shores and was raided. (The film contains technically the first British screen erection). Bertolucci lost ten-seconds of butter-smearing from 1972's Last Tango in Paris. Peckinpah returned with the brutal Straw Dogs (1971), only to have it subsequently banned on video. And Kubrick ushered in the first (and almost last) sightings of one of the great bug-bears of British censorship - the legendary A Clockwork Orange.

Hailed as both "a masterpiece" and "muck in the name of art" (both assessments appeared in The Sunday Telegraph), the film played - BBFC-approved - a full year on one London screen before being pulled by its director in what Mathews calls the "most effective banning in British film censorship". While it remains legally available elsewhere, A Clockwork Orange is unshowable here (evidence the 1993 prosecution of London's Scala cinema) and will be cut "deeply" if submitted on tape in the foreseeable future. (Ironically, profits for Kubrick's over-rated epic currently swell the coffers of video pirates nationwide).

Naturally any perceived liberalism has a corollary, and here it came in the shape of Mary Whitehouse's Festival of Light and other self-appointed moralists. Stephen Murphy replaced Trevelyan briefly before the appointment, in 1975, of current Director (formerly mere Secretary) James Ferman to smooth troubled waters. He did, imposing a new set of values to film censorship, albeit ones no less rigorous in their protection of the vulnerable. Most notably, Ferman moved to liberalise (non-violent) sex, a scheme all but short-circuited by local authorities moving to close down the very cinemas the new rules aimed to supply. The revival has only come recently via the influx of so-called 'educational' sex tapes. (However, Oshima's astonishing and explicit 1976 film In The Realm of the Senses [shown on elsewhere TV] finally gained a cinema certificate only in March 1991.)

Towards violence however Ferman is nothing if not a zealot, and the book paints a picture of a man almost single-handedly turning the Board - with increasingly absurd wielding of the censorial art - from supposed public servant into a private oligarchy. Seemingly cartoonish fare like Point Break, Terminator II, Cliffhanger and even The Bodyguard were all granted their current certificates only after cutting.

Faced with both possible BBFC bankruptcy and knee-jerk moralism, the 1984 Video Recordings Act and swingeing video censorship followed. The resulting surge of classifiable titles (more often than not, cut) filled BBFC coffers and it seems, ever increased Ferman's authority. (The Director himself imposed the new rule whereby the right to know how the Board reacted to any film after 1975 is solely at the discretion of the Director himself; Ferman's increasing public face goes hand in hand with increasing dominance.) Mathews documents the absurd banning of Freidkin's childish and overvalued The Exorcist (1973) for home viewing. ("It would better to pass it uncut," says Ferman, and as he feels unable to do so, it remains unavailable in any form). The progress of the astonishing Henry - Portrait of a Serial Killer (1989) through the machinations of the BBFC are numbing - the film on tape is short almost 2 minutes. The likes of Reservoir Dogs and Bad Lieutenant (both 1992), and True Romance (1993) currently reside in a video limbo.

And at the end of 1993, James Ferman took it upon himself to effectively dismiss all BBFC examiners by not renewing their contracts.

Censored is an intelligently argued, exhaustively researched and extensively illustrated work that arrives upon us with immaculate timing. If Mathews is serving an essentially liberal, anti-censorship agenda then it is never less than explicit throughout the eminently well-argued closing chapters. In its honesty and candour it is at least more trustworthy than the frustrating games being played in the offices of the BBFC. And unfortunately there is little in here to make the reader think Ferman is finished yet.