Chris Larner: The actor who helps his ex-wife die every night

Taking your ex-wife to commit suicide at the Dignitas clinic in Switzerland is not the sort of trip that most people would want to relive, yet alone profit from. But this week the playwright and actor Chris Larner will go on stage every night and tell a group of strangers about the day in November 2010 when his former wife Allyson swallowed the foul-tasting pill that killed her.

His play, An Instinct for Kindness, is unflinching in its description of Allyson's suffering from multiple sclerosis, which left her unable to walk and in constant pain. It is even more uncompromising in its portrayal of her final moments, right down to the last enema. The production received rave reviews when it debuted in Edinburgh last summer, and now it has reached London's West End, opening at Trafalgar Studios on Tuesday.

"I was in two minds as to whether it was inappropriate or prurient or just too grisly for me to tell this story," Larner, 52, admits, sitting barefoot in his ramshackle flat in Streatham, south London. "I've performed it about 50 or 60 times now. There are times when I think: 'Oh my God can I really drag this out of me again tonight?' But I seem to be able to."

He and Allyson had been divorced for more than two decades when she asked in 2008 if he would take her to Switzerland. They had remained friends but led separate lives – he an actor in London, appearing on stage and in television shows such as London's Burning, in which he played the character Clingfilm, and she in Otley, Yorkshire, working as a drama teacher.

He says she made the decision easy for him: "I don't think Allyson ever wavered from her conviction of what she wanted to do, and she didn't for one second ask for my permission or approval. Had she asked my opinion I wouldn't have known what to say."

Though he was breaking the law by helping her travel to the clinic, he has not been contacted by the police and was relatively unconcerned about it beforehand. "I did have a slight nervousness but I had friends and family that were more nervous than I was. Even then, 16 months ago, the police were increasingly embarrassed about being asked to investigate, arrest or prosecute people like me."

Their son George, now 28, understood what she wanted to do, but when the day arrived he decided not to go with them, instead calling and begging her not to go through with it. "Both Allyson and I talked to him extensively about the whole business before we went and he was in all ways in agreement with it philosophically and morally and politically. But when it came to it he just freaked out; his head said one thing and his heart said another. He simply wanted his mum to be back."

George has not seen the play, which charts the emotion of carrying on without his approval. "I don't particularly want him to see it," Larner says, "and he doesn't want to; he wants to be quite private about how he feels about his mum." Allyson's family are also unsure about the project. "My family are very proud of me for doing it, but Allyson's family are in two minds. Her sister Vivienne [who came with them to Dignitas] did see the show and reported back to the family that it was a good thing. I think they just find it a bit odd being so public with it."

One person who definitely doesn't want to see the play is his current wife, Julie, whom he married last year. "She's very proud of it but she hasn't seen it – she says it'd make her weep. There did come a point just after Edinburgh when a tour was mooted and there was a sense that Julie was thinking 'can we not move on?'"

Despite all the emotional upheavals of putting on such a personal show, Larner found himself desperate to continue: "Artists have always plundered their own and other people's emotions to make things and I flatter myself that the play has a certain beauty about it."

He is pleased that it is putting humanity into a debate on assisted suicide that has become very theoretical. "It addresses an emotional side to the problem that is not expressed in the high moral debate that's currently flying around the Lords. That does make me feel that there's a use in doing it which excuses me."

Larner is enraged by the current law, the effect of which is that every fortnight someone with a serious illness travels to Switzerland in order to be helped to end their life. Last month MPs endorsed guidance written by Keir Starmer, the Director of Public Prosecutions, which decriminalised some of those who help the terminally ill to commit suicide. But it is still illegal to help someone die in Britain. "The law needs to be changed. Suicide itself is decriminalised, so I could go to Beachy Head and throw myself off, but Allyson couldn't because her legs didn't work. That seems to me to be a rather cruel irony, that we allow suicide in the able-bodied but deny it to those unable to take such measures."

Allyson looked into other ways of killing herself, but Larner says she was just "too terrified" that if something went wrong she would wake up in a worse state than before.

Despite his convictions, the play does not rant about the iniquities of the law. In fact, one of its strengths is that there are times when the audience is prompted to doubt whether they are right to go ahead.

The night they arrive in Switzerland he describes Allyson and her sister Vivienne gossiping and enjoying time together, getting merry on red wine. At this stage was he not tempted to try to change her mind? His answer is a firm "no". "When her body allowed her to be she was a very positive woman, but her body was collapsing around her. I don't think I could've persuaded her."

Once Allyson had swallowed the pill that killed her, chased down with Swiss chocolate to sweeten the taste, Larner had to make the long journey home with Vivienne. "We had to struggle back on the plane with a wheelchair, which isn't allowed. They won't carry it unless you've got a ticket and a passenger, so we had to rather tragicomically battle with bureaucrats at Zurich and Amsterdam who were saying 'there's the ticket, but where's the bloody passenger?'. We had to say 'well, she's staying in Switzerland'. The whole business is a welcome mat for euphemisms."

Getting on with life afterwards was, he says, the hardest part for him and for Vivienne. "We felt like we'd travelled much further than a few thousand miles – we felt as if we'd been to another planet."

He believes sharing the experience has helped, though he admits it may have "elongated the grieving process". It certainly doesn't seem the easiest way to spend the first year of a new marriage, an accident of timing which he concedes is "a bit odd".

Larner was spurred on by the good reviews and public response, but he recalls how a friend summed up the problem with the play: "He said that as the lights were going down at the end he thought 'it's OK, because tomorrow Chris will get up and do the show and Allyson will be alive again'."

Curriculum vitae: An instinct for the stage

1959 Born in Harlow, Essex. Later goes to school at Burnt Mill Comprehensive.

1977 Attends Rada.

1982 Meets Allyson Lee at Theatre Centre in Manchester.

1983 He and Allyson marry in Didsbury Methodist Church, Manchester.

1984 Allyson is diagnosed with multiple sclerosis. Their son George is born.

1986 Allyson and Chris divorce.

1994 After several smaller TV roles, Chris begins a four-series stint as Clingfilm in London's Burning.

2001 Writes many comedy songs and musicals over several years; his song "Getting Out" is used in the Morecambe and Wise tribute show, The Play What I Wrote.

2008 Visits Allyson in Yorkshire, where she asks him to help her get to Switzerland and end her life.

2010 Travels to Switzerland with Allyson, where she commits suicide.

2011 Gets married to Julie. An Instinct for Kindness opens in Edinburgh, then tours regional theatres.

2012 An Instinct for Kindness opens at Trafalgar Studios, London.