‘Hard to watch’: a play about Harold Shipman by the grandson of one of his victims | Harold Shipman

He was a big man with a bushy beard and a bowl of sweets on his desk for good boys and girls.

This is all Edwin Flay remembers about Harold Shipman, whose surgery in Hyde he visited as a small child in the 1970s. The GP later became the UK’s most persistent serial killer, ending the life of about 250 of his patients.

Now Flay has written and performs in a one-man play about the mass murderer, whose victims included Flay’s grandmother. It will open at the Edinburgh fringe for a three-week run on 4 August.

The Quality of Mercy is described as a “psychological study” of Shipman, set in his prison cell the night before he killed himself. His death was celebrated by some newspapers, commentators and politicians.

Writing the play was a way of exploring his own “contradictory feelings about Shipman”, Flay said. “My grandmother was very ill and very unhappy when he took her life, and I am in principle in favour of assisted dying. But there was nothing altruistic in Shipman’s activities.”

Renee Lacey, Flay’s grandmother, was 63 and suffering from dementia and cancer when Shipman killed her. “She was frightened and disoriented. Shipman was talking about palliative care and the possibility of moving her to a hospice,” said Flay.

But a couple of days later, Lacey died unexpectedly. “Shipman had done a home visit. She was in bed. He came downstairs to tell my grandfather that her lungs were filling with fluid. In fact, he’d just given her a lethal injection.”

The suddenness of her death made Flay’s aunt suspicious. “She’d never liked Shipman – she always felt there was something off about him. She thought he might have done something to hasten her death.”

The truth began to emerge after Shipman’s arrest two years later, in 1998. Some of his victims had been close to the end of their lives, but others were in reasonable health when he killed them.

Flay supports terminally ill people being allowed to choose the time and manner of their death with help from medical professionals.

He said his father’s death had been “horrible to witness”, adding that people with “extremely debilitating diseases should have the right to a dignified death. But anything that’s involuntary is morally repugnant.

“Shipman obviously is an extreme example of how not to do it, but [his case] can also be used to raise the question of what better solutions exist. And the answer is we don’t have a good solution at present.”

In writing the play, Flay drew on the four-year public inquiry into Shipman’s killings, which produced its final report in 2005. It took evidence from four criminal psychologists, and considered witness statements from victims’ relatives – including Flay’s mother, grandfather and aunt.

“There’s a wealth of evidence out there, then you have to try to stitch together a convincing psychological portrait,” said Flay.

During his trial on 15 counts of murder in 1999-2000, Shipman – who denied the charges – chose not to take the stand, leaving his victims’ relatives with many unanswered questions. Flay believes he had a “God complex”.

But the trial and inquiry “changed the culture of deference to authority. People are less likely to put doctors on a pedestal,” he said.

Shipman was convicted and sentenced to life imprisonment. Four years later, he was found dead in his cell.

The Quality of Mercy had its first outing in London last year, which resulted in three nominations for Offies (Off West End theatre awards).

Playing the man who murdered his grandmother had been an “intense experience”, said Flay. “Shipman is not a nice person to play. I never came off stage feeling exhilarated or happy. And I think it’s a hard play to watch.”

The Quality of Mercy previews on 26-28 July at the Assembly Rooms theatre, Durham fringe festival before playing at the Edinburgh fringe at theSpace @ Surgeons’ Hall, Grand Theatre from 4 to 26 August.