"I volunteered to do this privately," the Oxford West & Abingdon MP told BBC News Online. "It was the Medical Research Council that asked me if I would take part publicly in the hope of attracting publicity for the issue."

This act is neither brave nor heroic... the bravery, if such a word is to be used, lies with the often dignified Aids patients in Africa dying from this modern-day plague

Dr Evan Harris MP

"They and I wanted to have the opportunity to draw attention to the serious problem with HIV in Africa.

As a politician, I'm also able to use my platform to put pressure on the government and other agencies to seek funding for research on Aids issues in the developing world generally."

Track record of support

As befits a Liberal Democrat, Dr Harris has a long track record of supporting liberal causes. He is an active supporter of the gay rights group Stonewall, of the anti-fascist campaign group and magazine Searchlight, and is a member of the Green Liberal Democrats.

Dr Evan Harris had early fears "of the disaster about to befall southern Africa"

But it was in the 1980s that he first drawn to the issue of HIV and Aids: "When I saw there was a great deal of intolerance and discrimination towards Aids and HIV. I found that irrational and hard to understand even back then, never mind now."

During his university years - he served as president of the Oxford Medical Students - he worked as an HIV/Aids telephone counsellor and health adviser.

He qualified as a doctor in 1991. It was as a junior doctor in the early 1990s that he first found himself witnessing young men dying from Aids.

"These were young deaths and even - especially - as a junior hospital doctor, I had not seen so many young men die in their prime in our all-singing, all-dancing hi-tech teaching hospital," he later said.

"I knew back then of the disaster about to befall southern Africa."

As well as pursuing his medical work he became an active trade unionist, becoming a British Medical Association negotiator and winning election to its regional council. He has long campaigned for an end to the long hours worked by junior doctors.

He currently sits on the BMA's medical ethics committee.

Family links to Africa

In the meantime his political career had been gathering pace. Dr Harris joined the SDP in 1985, moving to the Liberals the following year.

He became president of the Oxford University Alliance Society in 1986, and switched to the Liberal Democrats in 1988.

After the 1992 general election he acted as adviser to the Lib Dems' then health spokesman, Simon Hughes - who shares a number of leftish Lib Dem concerns with Harris.

When he made it to the House of Commons in his own elected right at the 1997 election, Dr Harris was an obvious choice for the party's frontbench health team. The party's last reshuffle saw him given the role of frontbench spokesman on higher education, science and women's issues.

As well as his wish to aid the discovery of an Aids vaccine, Dr Harris has been keen to highlight how the disease has ravaged parts of Africa.

He also has strong family links to the region. Though born in Leeds himself, he is the son of white South African immigrants who left their home having become disillusioned with apartheid.

"It is often argued that the developing world has been used as a testing ground for western medicines that are then out of reach to the poorest," he said on his own enrolment in the vaccine testing programme.

"In this case, it is noteworthy that this vaccine, if it works in Africa, will not work with the western strains of the virus, and that it is partnership between top scientists in the UK and in Kenya that has brought us this far."