In fact, the manufacturers were surprised by the number of men who asked for relief. The problem for so long hidden away proved to be far greater than anyone had guessed. For the manufacturer, this was the opening day for the gold mine. For men, it was the opening day of the rest of their active sexual lives. Researchers came rushing forward to start a host of new projects to investigate the causes of erectile dysfunction now that most men affected were prepared to talk about their problems. For two or three years, this new climate of honesty continued but then, to everyone’s surprise, the number of prescriptions stabilised and, in some countries, began to fall. The online pharmacies were establishing their credibility and offering a completely confidential delivery service without the need for a prescription. Now men could sit in their own homes and place an order with their privacy guaranteed. The problem went back underground and researchers found it difficult to recruit men for their latest projects.

There is good and bad in this. Viagra has proved itself a remarkably effective drug. In almost every case, this drug works the first and then every time to produce an erection when needed. For that, millions of men around the world are grateful. But for medical research, an opportunity has been lost. In the years immediately after viagra appeared, we learned so much more about the extent of the problem and its causes. Many changes have been made to the training of doctors and to the range of treatments available as a result. But with an increasing number of men buying the drug without seeking medical advice, the chance for collecting more information is reducing. If the trend continues, we will be back to the days of plausible deniability.