Simon was in an open prison when he started his combination drug therapy. But when he was transferred to another prison, his treatment stopped abruptly.
It is a typical case, according to Stephanie Sexton, convenor of the National AIDS and Prisons Forum, who says it happens because there are no national guidelines on the treatment of prisoners with HIV/AIDS.
The forum says many UK prisons do not offer combination therapy to prisoners who would benefit from it, although the proportion of people living with HIV/AIDS is higher in prison than in the general population.
Where the treatment is offered, the prison regime often makes it difficult to take the drugs. Some have to be taken every eight hours, or at other intervals that do not fit in with prison life. Some are taken after fasting, some with high-fat foods. But for the drugs to work properly, doses cannot be skipped or taken late.
The forum wants the prison service to ensure that all prisoners with HIV/AIDS have access to specialist medical care. They have been given new ammunition by the first official study of the extent of HIV among prisoners in England and Wales, which was presented to the 12th World AIDS conference in Geneva this month.
The survey found that women prisoners are nearly 13 times more likely to have HIV/AIDS than the UK population as a whole, and male prisoners are nearly four times more likely to be affected. That showed 'the urgent need for a systematic approach to culturally sensitive HIV prevention work' in prisons.
Conducted by Andrew Weild of the Public Health Laboratory Service and Len Curran of the Prison Health Service, the survey found that a high proportion of prisoners are at risk of HIV transmission in prison. It found that 41 per cent of adult men, 20 per cent of male young offenders, and 25 per cent of women inject drugs in prison, and 4.1 per cent of adult males reported having anal sex in prison.
Ms Sexton accepts that the sample was small: 2,100 adult males, 713 young offenders and 410 women. The researchers have also said that the sample, from seven prisons, was not representative of the prison population.
'But regardless of whether we will ever know exactly how many prisoners are HIV positive, what is important is that every prisoner with HIV has access to appropriate medical care and monitoring,' she says.
'If we take the study results as a rough guide, they indicate that at any one time there are over 200 prisoners in England and Wales who require HIV/AIDS specialist care. The prison service should send a clear message to prisons that such care is required and give prisons the tools that will help them.'
The prison service says there is no need for national guidelines 'because all prisoners are entitled to the same healthcare as any other member of the community'. Primary care services are provided by a medical officer of health within the prisons, secondary care by local NHS providers.
But Ms Sexton says 'there is a world of difference' between theory and practice. 'Many prisons have not established links with healthcare specialists in this field. Many are even denying that there are any prisoners with HIV/AIDS.
'There are no protocols and some say there is no budget for this treatment, although the cost of HIV/AIDS treatment should be borne by health authorities, not the prison service or individual prisons.'
David Walker, a consultant in communicable diseases with Durham HA, agrees that secondary services should be provided by HAs to ensure there is no financial barrier to prisoners' access to HIV/AIDS services. 'But I don't know how easy it is for prisoners to ask for these services,' he admits.
Andrew Ridley, director of operations with the Terrence Higgins Trust, believes it is essential that anyone with HIV has access to combination therapy 'regardless of where they are'. It is also vital that, once started on the therapy, they are kept on it, says Mr Ridley.
He also believes prisons should make it as easy as possible for prisoners to take their combination therapy drugs.
'Even people who live relatively stable lives in stable environments find it intensely difficult to adhere to complex drug regimes. For the population involved in the criminal justice system there is a case for even more support to help them adhere to the regimes.'