Whilst there has been huge speculation about changes in sexual behaviour over the last century, there has been surprisingly little rigorous research. The emergence of HIV highlighted an urgent need for such data and the National Survey of Sexual Attitudes and Behaviour (NATSAL) was created.
The first survey consisted of 18,876 interviews carried out in the UK between May 1990 and November 1991. It covered almost every conceivable area including the age people lost their virginity, homosexual experiences, and the number of sexual partners. It also looked for differences between demographic groups and attitudes towards sex and sexuality.
The results were fascinating, but it was the follow up survey in 1999-2001, which showed conclusively just how fast the sexual behaviour of people in Britain was changing.
Number of partners
For heterosexual men and women, the average number of lifetime partners had grown significantly between 1990 and 2000. On average, for men, it had grown from 4 to 6, and for women, it had doubled from 2 to 4. The number of people reporting one or no sexual partners in their lifetime had also decreased. Younger people (aged 16-24) reported the highest median average of partners for the last five years (3 for men, 2 for women).
Sex in the last four weeks
Researchers found that the number of sexual encounters in the previous four weeks was very similar for those questioned in 1990 and 2000. So we aren't necessarily having more sex - just sex with more people.
There has been a substantial change in the attitude to one night stands. In 1990 53% of men and 79% of women considered one night stands to be wrong. Ten years later the figures had fallen to 35% and 54% respectively. However, Britain remains highly intolerant towards extra-marital sex. Indeed there was a slight increase in hostility to affairs for both men and women
Losing your virginity
In 1990, the average age for losing one's virginity was 17 for men and 18 for women. Ten years later it was 17 for both men and women. Notably, there was a doubling of the proportion of women who reported first intercourse before 16 years of age - from 10.3% to 20.4%. For men the figure rose from 20% to 27%
The agony aunt's experience
The facts come as no surprise to Britain's most widely read agony aunt, Deidre Sanders. Her page in The Sun has been running for 25 years, and is the second most read part of the newspaper. She gets 800 letters and e-mails a week, and has seen a big change in her mailbag since she began.
Deirdre Sanders of the "Dear Deirdre" column is a top agony aunt
"From younger people, they used to be quite simply na´ve questions really. They might be worries about their body or how you get to know a boy or girl. I still get inquiries like that but also now from that same age group I'll be getting much more heavy-duty questions."
"It was all summed up for me by one... which is a 16-year-old girl involved with an 18-year-old boy. She wanted to lose her virginity in a threesome with another girl, and it's actually the boy writing to me because he's a bit worried about what he's getting involved in."
"It was absolutely inconceivable when I started this job, that you'd have a 16-year-old girl thinking about a threesome."
Deidre is shocked by the continuing levels of ignorance about protection. She believes passionately that relationships and sex education should be taught at an early age, and that it should be compulsory. "I'm surprised to find myself saying this, but it does appear that the situation is even worse."
"For example I had a letter from a young guy who was gay and he had no idea about HIV, how it's transmitted, how you protect yourself against it, and you just think... how has he managed to get through to that age and no one has got that information through to him?"
And Britain's most read agony aunt is worried not just about the physical consequences about our sexual behaviour - but about the long term emotional effects.
"I think there's a whole generation, or generations of young people who are not happy with this, they're not having a good time, they're picking up infections which are going to damage them physically, some of them aren't going to know that they're not going to have children as a result of this, they're not having good sex, they're not enjoying this, they're not having relationships they're finding rewarding."