This dual Blu-Ray and DVD release costs £13 at the moment. The BFI seems now only to be releasing new titles in this irritating dual format, which feels like a rather shoddy attempt to get people to pay extra. I did not need a DVD of this film, as I can watch Blu-Rays. If I didn't have a Blu-Ray player, I'd probably feel more than a little irritated at having to pay extra for a Blu-Ray disk I didn't want.

This annoyance has rather taken the gloss off what is otherwise one of the most welcome releases for years. Deep End (1971) is a lost classic, a film that met with acclaim at the time of its release but has since disappeared, apparently the victim of a rights issue. It's only been available in dodgy bootleg copies or illegal downloads, so it's definitely great to see it finally get a proper release.

Mike is 15 and just out of school. He gets a job as a bath attendant at the local swimming pool. He rapidly becomes obsessed with his sexy colleague, Susan, and begins stalking her, even though she's already engaged.

The film is one of the most excruciating examinations of what it is to be a teenage boy that I've seen. Mike's sexual obsession with Sue gradually takes over his whole life. The way he reads enormous significance into everything she does and clumsily intrudes on her life should be horribly familiar to anyone who ever had a teenage crush. Sue plays up to this, teasing and flirting with him, although it's never clear whether she really has any feelings for him beyond simple friendship. She's taking the traditional route to success, engaged to a well-off man she doesn't seem to like very much, while also carrying on with an older, married man.

For the most part the film plays out as a comedy of embarrassment, with Mike's antics funny because they're so familiar. But there are hints at something darker throughout (all those suggestive splashes of red paint), and the ending is unexpected and brilliant, even if it's a bit sudden. The film was made by a Polish director, although set in London, and like Roman Polanski's classic Repulsion, it seems to show us something about British society that we natives don't really notice. The film's version of Swinging London is a grotty Soho street corner of flashy nightclubs, tatty sex shows and homely prostitutes. The sexual revolution consists of bored middle-aged housewives getting their jollies by molesting teenage boys, or swimming teachers feeling up schoolgirls.

The film uses remarkable locations, like the aforementioned Soho street corner. The swimming bath, shot in two public baths, one in Munich and one in Leytonstone, is fantastically dilapidated, with cleanliness and wholesome exercise seemingly the last things on anyone's mind. The peeling but still bright paintwork gives a magnificently flaky aspect to the film, which is backed up in pretty much everything else we see. Was the country really so shabby in 1970? Even the porn film Sue's classy boyfriend takes her to see is hilarious - 'The Science of Sex', an amusing pastiche of the kinds of continental pseudo-documentaries that were briefly popular as stroke material for England's lonelier bachelors.

The film's greatest asset is Jane Asher as Susan. Although nowadays she's a mumsy cake maker, this is still sexy 60s Asher, the former Beatle girlfriend. She's remarkable as the sexy but hard-nosed bird on the make, still naive enough to hang around with her older lover, but pragmatic enough to marry well. She has a casual attitude to sex, but doesn't seem to be terribly interested in it. She even manages a convincingly common accent. John Moulder-Brown, who never quite made it, is also great as Mike, perfectly capturing adolescent awkwardness (he was only 17 at the time, so probably no great stretch). His main problem is that his voice sounds far too posh for him to really be working in a bathhouse in Leytonstone, but it adds an oddly surreal, distracted quality to the film.

This quality is also found in the other characters. Most of the rest of the cast are German, with various English accents dubbed onto them (the film was mostly shot in Germany). The voices match the lip movements well enough, but it's often distractingly obvious that they're not really being spoken by the actors on screen. There are a few English cast members apart from Mike and Sue. The annoying fiancé is played well by Christopher Sandford, and Burt Kwouk makes an amusing cameo in the Soho sequence. Diana Dors has an unforgettable scene as a woman getting off on a fantasy about football, with the deeply reluctant Mike having to stand in for George Best. Every encounter Mike has with a woman seems to be designed specifically to make him even more neurotic about sex.

The film makes great use of Mother Sky, a classic track by krautrockers Can, and everything else is very professionally done (apart from a few blurry shots - almost all the camera work is handheld). But it's the ending that really defines the film, and while I can't give it away here, it's probably not what you'll be expecting.

This used to be an X-rated film; it's a sign of how far we've come that it's now a 15. There's a fair bit of nudity, including a few full frontal glimpses of Jane Asher.

The film on Blu-Ray looks pretty good. There's a bit of grain to the image, and it occasionally looks oddly flat, possibly because of whatever digital noise reduction software they've used. But it does the job well enough; the colours are especially vibrant. Given the shoddy quality of the copy I had previously, it can't help but be a huge improvement.

The best extra is a long (74 minutes) making of documentary featuring the director and main cast, along with various other personnel. It's interesting, especially to learn which bits were shot where, but it's a bit too grown-up, with everyone talking jolly seriously about how marvellous it was to make and how proud they are of it. There's a shorter piece about some of the scenes which were shot but cut out, although sadly the scenes themselves aren't available.

We also get a trailer and a short film called Careless Love in which Jane Asher goes to extreme lengths to keep her lover. It's pretty creepy, although suffers from spelling out what's going on a bit earlier than it really needs to. The extras are in HD as well, although the visual quality on the trailer and Careless Love is poor. There's also a booklet containing various critics' and film historians' musings on the film.

The DVD version has exactly the same extras as the Blu-Ray. The picture quality is perfectly decent - in fact it doesn't feel like there's too huge a leap between this and the Blu-Ray version. To be honest, I'd have been perfectly happy with just the DVD. But I strongly resent having to buy both. That bumps this down to the three-star review.