The man who may hold the key to a cure for Aids was urged by doctors last night to come forward for the sake of millions of virus carriers worldwide.
The case of Andrew Stimpson, 25, who was diagnosed as HIV-positive in 2002 but found to be clear of the virus in 2003, has stunned the medical world. If doctors can establish why this happened, without treatment, it could benefit the 34.9 million virus carriers worldwide.
But Chelsea and Westminster Healthcare NHS Trust, which carried out the initial diagnosis tests, said Mr Stimpson has so far declined to undergo further tests with it.
A spokeswoman for the Trust said: "I can confirm that he has a positive and a negative test.
"When we became aware of his HIV-negative result we offered him further tests to help us investigate and find an explanation. So far he has declined to do so."
Mr Stimpson subsequently tried to sue the hospital, believing his initial positive test was inaccurate. But he was told there was no case to answer because both tests were correct. The Trust spokeswoman insisted there was no chance a mistake had crept into the testing system.
Mr Stimpson told the Mail on Sunday: "My doctor said 'you've cured yourself, you're fantastic'."
"I can't help wondering if I hold the cure for Aids. There are 34.9 million people with HIV and if I have something to contribute, then I am willing and ready to help."
The Scotsman, 25, who moved from the Ayrshire village of Skelmorlie, near Largs, to London four years ago, did not take any medication for HIV.
Genevieve Clark, the director of communications at the Terence Higgins Trust, said: "For this to happen is unheard of. We are not aware of any similar cases in the UK.
"The news is potentially remarkable but raises a lot of questions. There needs to be a thorough, scientific investigation to find out exactly what has happened.
"The fact that the hospital doctors are keen to do more tests shows it is early days. It could be a major breakthrough but we are keen to know more."
Mr Stimpson, who works as a sandwich maker, caught the virus from his long-term partner, Juan Gomez, 44, who has been HIV positive for some years.
Mr Stimpson felt tired, weak and feverish in May 2002. He had three blood tests at the Victoria Clinic for Sexual Health in west London, which specialises in HIV.
At first they were all negative, but Andrew was told the virus takes three months to show up in the blood after contraction.
And when he returned for more tests in August, they found HIV anti-bodies in his body.
Mr Stimpson said he became depressed and suicidal after being told he was HIV-positive but remained well and did not require medication.
"One thing I decided early on was I never wanted to see the HIV through to Aids. I was having nightmares about being in intensive care, hooked up to tubes and covered in lesions.
"It got so bad that I began researching euthanasia as a possible way out."
In the months following the diagnosis, Mr Stimpson complained of feverishness and other flu symptoms. But his doctors told him his body was "controlling" the virus well and that his immune system remained strong.
However, in October 2003 during a routine appointment at the Victoria Clinic, a doctor suggested a more sensitive test to check his viral load. It came back negative. Three more tests came back the same.
"There was a massive relief but I was also deeply confused," said Mr Stimpson. "And the doctors seemed as confused as me. I thought the first positive tests must have been wrong." But an investigation by the trust claimed otherwise.
Dr Patrick Dixon, an expert from Acet, an international Aids group, said the case was "very, very unusual. I've come across many anecdotal reports of this kind of thing happening in Africa, some quite recently, but it's difficult to verify them," he said.
"You have to be rock-solid sure that both samples came from the same person, no mix-up in the laboratory, no mistakes in the testing. This is the first well-documented case."
The case was important because "inside his immune system is perhaps a key that could allow us to develop some kind of vaccine".
The news will bring hope to millions dying of Aids who could benefit if medical scientists discover how Mr Stimpson's medical status changed.
Lisa Power, the policy director at the Terence Higgins Trust, said: "This could be of major interest to HIV researchers. We need to find out precisely what's happened with this person."
HIV and Aids: The facts
* HIV is the fastest growing serious health condition in the UK.
* Around 63,000 cases of HIV reported since it was discovered in the early Eighties
* 3,802 Aids-related deaths in total
* 6,675 new diagnoses in 2003
* 4,706 new diagnoses reported so far for 2004, but this is expected to rise to around 7,000 when all the data is compiled
* Men living with HIV outnumber women who have HIV by 2:1
* 47 per cent of new cases of HIV in 2003 were in London
* 52 per cent of people with HIV in 2003 live in London
* At the end of 2004, an estimated 39.4 million people had HIV
* 4.9 million people were infected with HIV in 2004 and 3.1 million people died from Aids-related illness
* The number of new cases diagnosed in East Asia rose by almost 50 per cent between 2002 and 2004, due mostly to China's rapidly growing epidemic.
* In Eastern Europe and Central Asia, diagnoses rates were up by 40 per cent between 2002 and 2004, mainly because of increases in the countries of the former Soviet Union.
* Sub-Saharan Africa continues to be the worst affected region, with 25.4 million people living with HIV at the end of 2004, up from 24.4 million in 2002.
* Sub-Saharan Africa accounts for nearly two-thirds (64 per cent) of all HIV infections worldwide. Three-quarters (76 per cent) of all the women living with HIV live there.
Source: Terrence Higgins Trust.