The next two columns (E and F) come from the same data set, the UK Gay Men’s Sex Survey of 2003. They represent (E) the proportion of gay and bisexual men who said they had not had unprotected anal intercourse with anyone over the last year (60.2 per cent) and (F) the proportion who said they had ‘probably or definitely’ not had unprotected sex with someone of a different HIV status (69.3 per cent).

The nine per cent difference between these two figures represents people who were pretty sure they were having unprotected sex with people whose HIV status was the same as theirs, and were therefore not at risk of being infected or infecting someone with HIV (though they were at risk of other STIs). It might be asked how these men knew their partners’ HIV status and whether many in that nine per cent were people making wrong assumptions about their partners’ HIV status.

But this nine per cent also excludes the 24 per cent or respondents who were less certain about whether they’d had unprotected sex with a person of differing HIV status. Only 10.3 per cent of the men in the survey were fairly sure that had had serodiscordant unprotected sex, and thus represent the highest population at highest risk of HIV acquisition or transmission.

In recent years the emphasis on condom use has tended to change from a blanket insistence on 100 per cent condom use to a much more nuanced recognition that decisions as to whether or not to use condoms are often arrived at through a complex series of assumptions, calculations and conversations between people. This is discussed in the next section on disclosure, serosorting and negotiated safety.

However this is not an uncontroversial shift in emphasis. In the same way as opponents of condom distribution say that providing condoms only encourages more sex, some prevention experts worry that supporting harm-reduction strategies such as trying to only have sex with people of the same HIV status (‘serosorting’) spreads confusing messages and encourages people to rationalise about having unsafe sex. More on this below.