In contrast to its subsequent reputation, The Killing Of Sister George has very reputable antecedents. A successful stage play by British author and Daily Telegraph theatre critic Frank Marcus, it had been performed both in London’s West End and on Broadway. The play won the Evening Standard Award for Best Play in 1965, while Beryl Reid’s performance (she played the central role on both sides of the Atlantic) won the Tony Award for Best Dramatic Actress in 1967.

The play and film charts the unravelling of the professional and personal life of a middle aged actress. June Buckridge (Beryl Reid) plays district nurse Sister George in 'Applehurst', a popular BBC TV soap opera set in an idyllic English country village (reportedly based on the long-running 'The Archers' radio show). In contrast to her kindly aphorism-quoting character, June is a volatile, temperamental, gin-swilling woman prone to emotional outbursts, drunken jealousy and an inappropriate sense of mischief. June has a ‘flatmate’, an attractive much younger woman Childie, with whom she has an occasionally abusive relationship. An incident in which June drunkenly accosts two novice nuns in the back of a black cab brings her behaviour to the attention of BBC television executives, in particular Mrs Mercy Crofts. From this point, things start going wrong for June and it becomes apparent Mrs Crofts has a hidden agenda.

The hefty BBFC file on the film's classification (running to three files) is testament to the contentiousness of its theme and to prevailing sensibilities about some aspects of its portrayal of homosexual characters. Although the film is now regarded as a pioneering ‘lesbian’ classic, when the film was first submitted at the beginning of 1969 the initial opinion of the Board was less enthusiastic.

For the most part, The Killing Of Sister George was felt to be suitable only for the X category, the most restrictive certificate at the time (it limited cinema audiences to those aged 16 years and over).

The reports indicate that the 'theme' of lesbian relationships was considered an acceptable one for film-makers to tackle even though it may be ‘distasteful for many audiences’. There was some discussion about June’s aggressive utterance of ‘piss off’. The scene in which June forces Childie to eat a half-smoked cigar was ‘unpleasant’, but by the way it was presented within the film, it was also ‘acceptable’. It was the film’s penultimate scene in which Mrs Crofts seduces Childie which caused the Board considerable pause for thought.

In this sequence, Mrs Crofts is helping Childie gather her things to stay at her house after a final argument with June. The two women embrace. Childie removes her top and lies on the bed. Mrs Crofts approaches the bed and masturbates Childie to orgasm below screen before the couple are suddenly aware of June’s presence in the bedroom doorway. The sex scene was described by John Trevelyan, the then BBFC Secretary as ‘by far the most explicit scene of Lesbian physical love that has ever been submitted [for classification]’.

While lesbianism had never been illegal in the UK (male homosexuality had only been decriminalised two years earlier), the subject remained very much taboo. BBFC principal officers judged that the sex scene would not be harmful, in that it was unlikely to corrupt adult cinema goers, but were concerned that the public was not ready to accept such a detailed lesbian scene. The view was expressed in reports that the public would be ‘shocked’ by the scene to such a degree that it may prove detrimental to the ‘liberalism of film censorship’. John Trevelyan acknowledged that the BBFC had not been ‘ungenerous’ when allowing ‘passionate scenes of this kind’ to be passed in other films ‘but only when the relationship was heterosexual’. He further clarified this particular viewpoint in a letter to Cinerama, the film’s UK distributor. In explaining the decision for cuts Trevelyan said "... it is a totally different matter when the context is one of Lesbian physical love".

There was also the feeling at the BBFC that this scene was superfluous – ‘not dramatically necessary’ - to the wider film, and so removing the scene would not damage the narrative continuity or impinge on the film’s artistic qualities. There was a further concern that the scene could be used for sensationalist publicity purposes to promote the film. John Trevelyan pointed to reports from the States that cinema-goers in New York, where The Killing Of Sister George had been released with the sex scene intact, were contacting cinemas showing the film to find the exact time when this particular scene would appear. Taking all these factors into consideration, the BBFC asked the distributor to remove the sequence before it would issue a classification certificate to the film.  

Cinerama resisted the cut. A modified version of the scene was submitted for consideration, and then another version with further modifications. The distributor fought hard to retain the kiss between Mrs Crofts and Childie, citing a similar kiss in The Fox passed by the BBFC in 1967. But the BBFC was adamant that the scene be removed in its entirety. Trevelyan stated that the BBFC was ‘not prepared as yet to accept Lesbian sex to this point’.

The Killing Of Sister George was eventually classified X in February 1969 with the encounter between Mrs Crofts and Childie deleted. Nevertheless, the film was banned by a number of local authorities across the UK even in this version. The Greater London Council, however, was shown the uncut version of the film, and required only minor edits to the scene that the BBFC had deleted, thus allowing a more complete version of the film to be screened in its cinemas. The increase in the age bar for X films from 16 to 18 in 1970 saw some local authorities relent on their previous decision, and allow the film to be shown under this higher age restriction.

Later BBFC views on The Killing Of Sister George, when the film was submitted for video classification in 1986, were more sympathetic and demonstrated more relaxed attitudes towards on-screen depictions of homosexuality. One examiner described the scene between Mrs Croft and Childie as ‘tenderly portrayed’, while another recognised that the film would have been treated ‘less nervously’ if it had depicted heterosexual sex. The sexual orientation was considered less relevant to the classification of the film for VHS in 1986 than in 1969. However, the intensity and sexual detail of the sex scene still required the 18 category.

The film was classified most recently in 2001, with an 18 rating.