The Lover's Guide does pretty much as the title suggests - provides a guide for lovers. The documentary is laid out in chapters (like a manual) detailing various topic such as: contraception, exploring each other, sexual positions etc. The video is designed to educate and help couples either get over their inhibitions or to improve their sexual technique.
The video is a censorship milestone in the UK, possibly being one of the first (if not the first) film(s) to pass "hardcore" sex at 18 certificate. Hardcore being real sex, aroused genitals etc. The video went on to sell vast amounts (I heard 1,000,000 copies - an exaggeration?) largely on the premise that it offered the viewer explicit sex. As a result it was snapped up not just by couples but anyone who wanted to watch a bit of "smut". Another point is at the time of release many R18 sex shop only films were heavily cut and as a result possibly less or equally explicit.
One criticism I have of this video and many more like it is the emphasis is on couples and relationships. It seems sex education video makers frown on sex outside a loving relationship and I have no idea why. Still, The Lover's Guide does what it does well, despite being ludicrously outdated it may offer some good advice although I'm sure most couples already know what is discussed in the video. Worth a watch if only for curiosity.
