In a cold and dilapidated rehearsal room on the City of London outskirts, five men in blindfolds are being led on lengths of thread by five others. On the floor are sheets of paper covered in bread arranged into sculptural shapes.

This a rehearsal for A Tender Subject, a play/installation by artist and director Mark Storor created with gay male prisoners – a vulnerable, often invisible group who are rarely officially recognised.

From 16 March, in a short run in a secret location, audiences will walk through an installation led by actors playing prison officers and, says Storor, experience moments of tenderness in the gay prisoners' harsh lives.

Bread is important in jail, says Storor. "Lots of men end up with loaves of Mothers Pride in their cells – the brand has the contract for prisons. It's currency, you can play games with it, it's comforting. We're making a giant bread prison cell which will be about trying to somehow protect yourself, to give yourself comfort, but of course it's futile."

Three years in the making, A Tender Subject was commissioned by Artangel, famous for producing art outside galleries including Rachel Whiteread's House and Jeremy Deller's recreation of the Battle of Orgreave.

Storor had worked with prisoners before on a project called Boychild. When Artangel asked him to make a work exploring utopia in places perceived as violent or difficult, that experience, with his own sexuality, inspired him to work with gay prisoners.

However, says Rachel Anderson, head of interaction at Artangel: "When we asked Wandsworth prison services 'Can we work with gay men?' in the first meeting they said 'There aren't any'."

Most gay prisoners, she says, keep their sexuality quiet for fear of homophobic violence. "An openly gay prisoner would be famous on the prison scene."

Gradually, with the help of the support group Gays and Lesbians in the Prison Service (Galips), Anderson and Storor located gay prisoners who would participate. First the Galips rep in HMP Wandsworth issued a diversity questionnaire. Out of 460 replies (40% of the prison) 25 men identified as gay, which persuaded the governor the project was worthwhile.

Workshops were also set up in two other prisons, Doncaster and Parc in Wales. Storor and Anderson worked for seven weeks in Doncaster for two days a week – one with prisoners and one with prison staff.

"It was a big statement from the prison service to show that they fully supported people being openly gay in prison," says Anderson.

"Working with prison officers was a way of letting people know about the project and getting to understand that it was non-threatening," says Storor.

"We did a radio interview which went out to the prisoners and put up posters. We didn't say 'Are you gay, do you want to come and do a workshop?', it said 'Are you against homophobia?' "

The sessions were emotional, reducing even hardened prison officers to tears. "One member of the senior management team's family had broken up and he was looking at an image of one man lying down next to another," says Storor. "He interpreted that as the moment you're trying to find answers from yourself – how it could have been different."

Storor collated the stories into a work which will be performed by actors from the Only Connect theatre group, which works with former prisoners and young people regarded as at risk of offending. Most of the cast have been in prison, though none, to the knowledge of Storor and Anderson, are gay.

Storor and Anderson are at pains to point out that A Tender Moment is about intimacy, not sex. "When we said we wanted to work with gay men, people would tell us about rape," says Anderson.

"In prison, it can be accepted that men have sex with each other, but what can't be accepted is that men share the same moments of connection and tenderness in such an important way as a man and a woman do."

Anderson believes that A Tender Subject is a "pivotal work" for Artangel which has wide-ranging implications for the arts in Britain.

"Its roots are in educational practice, it articulates itself through social value and through the value of those participating in the process but it stands in a mainstream arts framework."

Though Storor's previous work includes For the Best, made with terminally ill children at the dialysis unit at the Evelina hospital school in Southwark, south London, he says that A Tender Subject was his most challenging project yet – not only in persuading the prison officers that it was worthwhile, but also in the work's nature, trying to find moments of intimacy in a world where violence and fear are far more common.

Jacques Le Vene, national chair of Galips, said projects like this were important for both staff and inmates.

"Everyone was treated as having something to offer the project. You can take a prisoner who's quite withdrawn, and through work like this can prove they have skills, a story to tell and leave prison with a better view of life and not have to turn to offending again. The staff begin to see the person behind the prisoner, which doesn't happen enough."