Sadomasochism is common. In his first report on sexual behaviour in 1948 Alfred Kinsey claimed that 50 per cent of respondents claimed to get erotic pleasure from being bitten, but the figure is probably nearer one in ten - and it's found equally in women and men.

A long line of research has indicated that it is higher-educated, Times-reading types who are more likely to indulge than those News of the World aficionados. I suspect a research bias here - Times readers are more likely to have the cash to spend on psychoanalysts who write research papers.

S&M behaviours can be psychological and physical. Although some people might place S&M in the same category as abuse, the important point is that it should be consensual.

There is no evidence that it leads to violent crime, although it can lead to embarrassment. A common form is to leave someone naked, defenceless and tied up. Fine if your leather-clad whip-wielding Zorro finds you. Bit of a bummer if it's the cleaning lady, your children or, worst of all, a tabloid newspaper...