This month it was revealed that US academics, funded by the National Institutes of Health, infected mentally incapacitated patients, prisoners, sex workers and soldiers from Guatemala with syphilis, gonorrhoea and chancroid during the 1940s.

There has been outrage, rightly. Since that time, regulations on consent have been tightened. But it's interesting to see who participates in medical trials today, and whether we would regard them as giving fully informed consent.