It is like one of those awful, cruel fairy tales by Hans Christian Andersen or the brothers Grimm. It deals with one of the most frequently recurring themes in literature. The possible variations are limitless. Two people, brother and sister, brother and brother, twins, or two people not known to each other at all, are born at the same time. If they are twins, they might become separated only to meet again later without knowing who the other is. As I say, there are endless variations.

Here is one: in November 1989 a good friend of mine, a stage designer, was told that he was HIV-positive. When his male partner underwent tests and was found also to be infected, they were soon able to work out what had happened. They were frank with each other and with their friends. The stage designer's partner had visited New York in the spring of 1988. He had been careless one night and invited a man he'd met in a bar to his hotel room. There was no other possible source of infection. A one-night stand, death the outcome. Despite the fact that one of them was clearly guilty of making them both carriers of the disease, they never – as far as I know – uttered a single angry word to each other. They both knew the risks. One of them had taken a chance. At that time, in the late 1980s, there were no ARVs. There was no hope at all, in fact. Death would ensue. Soon.

They began to make preparations. Or rather: they decided to live life to the full, to do everything they had planned to do, to cut out everything that was unnecessary. They moved from the town where they lived, settled in the country, and lived a quiet but intense life. I don't know much about their nights and their dawns: they must have been suffused with fear. Then they died, one of them in 1996, the other a year later.

A few years earlier, a woman friend of mine in Mozambique told me that she had Aids. Well, she didn't actually tell me at first, but I had started to suspect as much when she suddenly started losing weight, acquired a nasty cough, and lost a lot of her good humour. We knew each other well enough for me to ask her outright: had she tested positive? She confirmed my suspicions. When we went on to talk about it, she admitted that she had started living on borrowed time. She learned for certain that she had the disease in the spring of 1988.

She didn't last long after she told me that she was ill. Although I was able to help her financially, the resources available in Mozambique were inadequate to ease her suffering. Her death was dreadful. Unlike the friends I had in Sweden who were able to die without needless pain, one of them in an ordinary hospital, the other in a hospice.

All three died on the wrong side of the border, as it were. Before this happened, there were virtually no ARVs: afterwards, the new medication could give hope to the sufferers. The researchers and doctors had almost reached the first of the finishing lines. Only a year or so later it began to be possible, in the West, to slow down the progress of the disease. Nowadays, people with Aids live comparatively normal lives. A lot manage to die of other illnesses, or simply of old age.

But this development would have made a difference only to my two Swedish friends who died. The ARVs would not have been available to my friend in Mozambique. At least, not unless I had paid for them.

That makes me angry. A desire to overturn the injustice must survive the death of its victims.

In the early 1990s, at the theatre where I work in Maputo, we staged a production of We Can't Pay? We Won't Pay!, a play by Dario Fo that has been performed successfully all over the world. In it, a coffin is used to smuggle sacks of flour past a number of watchful police officers. The old carpenter, Mestre Afonse, made the coffin we used from thin plywood. Heaven alone knows where he managed to find this relatively rare but very useful material in Maputo. Anyway, we performed the play many times and then put the production in mothballs as we intended to include it in the repertoire at some future date.

And that is precisely what we did. Two years after the premiere our theatre manager, Manuela Soeiro, decided that it was time to give the Fo play another run of about a month. He spoke to me and we arranged times for rehearsals and reallocated one of the parts, since one of the actresses was much too pregnant to manage her part.

The day before we were due to rehearse the scene which involved the coffin I was approached by Alfredo, the stage manager, who asked for a word in private. He was very worried, and stared at his feet. I had great difficulty making out what he was muttering. In the end, the penny dropped.

"Are you saying that the coffin has disappeared?"

"Disappeared."

"How is that possible? It was agreed from the word go that this production would have a second run."

Alfredo stammered and mumbled away. I started getting impatient.

"For Christ's sake, that coffin can't simply have disappeared, can it?"

"It has been used."

"Used? What do you mean, used? What for?"

"For a funeral."

I stared at Alfredo for quite a while. Then we sat down in the front row of the stalls. I asked him to tell me the full story. A girl who used occasionally to hang around outside the theatre had died. She was seventeen or so and used to beg for food. She had died of Aids, Alfredo knew that for sure. He also assured me that although the girl probably worked as a prostitute, none of the theatre workers had been with her in that capacity.

But it was all to do with the burial. The girl did not have any relatives. She had run the risk of being tipped into one of the paupers' graves in the city. They were filled once a week with dead bodies. Then the stage technicians at the theatre had remembered the coffin that had been used in the Dario Fo play. It might only be a stage prop, a cheap plywood box, but it was better than nothing. So the coffin had been retrieved from the stores and the girl had been buried in a dignified way, though her coffin was only a prop from a play written by an Italian master of farce.

When Alfredo had finished his story, we sat there for ages, neither of us saying a word. I felt sick. It was as if reality had placed its heavy, gnarled hand over the theatre.

But the queasiness passed. I told Alfredo that I thought they had done the right thing. No doubt it would be possible to build another coffin.

"Mestre Afonse says he has no more plywood."

"Then he'll have to use something else."

"He has only solid wooden planks."

"Then he'll have to use those."

"They are thick planks. The coffin will be very heavy."

"Then the actors who carry the coffin will have to get used to that."

About a year later, Alfredo and I were both present at a burial service in the big cemetery outside Maputo, by the side of the road leading to Xai-Xai. Afterwards, as we were walking towards the gate, Alfredo pointed towards a corner of the cemetery. There were several mounds with no crosses.

I understood without him needing to say anything.

That was where she was buried, in a stage coffin made of plywood which had been used in a theatre production.

I've often thought that I ought to write to Dario Fo and tell him this story. I'm sure he would have liked it. I'm certain he would have been moved.