After the cells had been activated in this way, HIV pioneers found some 30 proteins in filtered material that gathered at a density characteristic of retroviruses. They attributed some of these to various parts of the virus. But they never demonstrated that these so-called "HIV antigens" belonged to a new retrovirus.

So, out of the 30 proteins, how did they select the ones to be defined as being from HIV? The answer is shocking, and goes to the root of what is probably the biggest scandal in medical history. They selected those that were most reactive with antibodies in blood samples from Aids patients and those at risk of Aids.

This means that "HIV" antigens are defined as such not on the basis of being shown to belong to HIV, but on the basis that they react with antibodies in Aids patients. Aids patients are then diagnosed as being infected with HIV on the basis that they have antibodies which react with those same antigens. The reasoning is circular.

Gay men leading "fast-track" sex lives, drug addicts, blood product recipients and others whose immune systems are exposed to multiple challenges and who are at risk of Aids are much more likely to have raised levels of the antibodies looked for by the tests than healthy people – because the antigens in the tests were chosen on the basis that they react with antibodies in Aids patients. But this association does not prove the presence of a lethal new virus.

The tests do discriminate between healthy blood and the blood of patients with Aids or Aids-like conditions, because Aids patients suffer a range of active infections and other blood abnormalities, some of which are transmissible. This is why the tests are useful as a screen for the safety of blood supplies.

But to tell even one person that they are HIV-infected on the grounds that they have antibodies that react with the proteins in these tests is an unwarranted assault.

Neville Hodgkinson is a UK-based journalist who has been writing about Aids for 20 years. He is the author of AIDS: The Failure of Contemporary Science (Fourth Estate, 1996).