Jimmy’s still taking on the Establishment...

As an acclaimed scriptwriter with a keen sense of justice, Jimmy McGovern is contacted from time to time by people who want him to tackle wrongs in their lives.

After decades in the business, the Liverpudlian – whose work includes the Bafta-winning Hillsborough and Bloody Sunday docudrama Sunday – is “armed against these things now”.

“I have a stock response which is, ‘I’m too old and too tired, I’ve packed it in now and I’m retiring’,” the 64-year-old says.

But when one woman’s letter arrived a month late having been wrongly addressed, McGovern thought it would be rude not to pick up the phone and explain his delayed reply.

The sender’s nephew had been imprisoned under the controversial joint enterprise doctrine, in which more than one person can be convicted of a murder even if the fatal blow was delivered by only one of them.

After hearing her story and that of other campaigners (“I phoned her and established a human contact, and then I was sucked into it...”), McGovern was moved to put pen to paper.

The result is powerful new BBC drama Common, a one-off film which explores joint enterprise through the fictional tale of Johnjo O’Shea, a 17-year-old in the north west of England.

We see the teenager, played by Mancunian actor Nico Mirallegro, give his friends a lift to a pizza parlour, unaware that they plan to confront a local lad inside.

A fatal stabbing ensues and Johnjo finds himself driving his friends away from the scene. Unable to prove he had nothing to do with the crime, he ends up facing a murder charge with the rest of them.

“Joint enterprise is bad no matter what the crime, but when it’s murder, it’s particularly bad because those who play smaller parts in a crime get entangled in the same net as the main players,” says McGovern, who wants to see reform of the law.

“Because it’s murder, the judge has no flexibility. So the sentence is the same: life.”

At a read-through of the script in Liverpool Town Hall, campaigners and members of the cast (which also includes actresses Jodhi May and Susan Lynch) ended up in tears.

A poignant moment, but McGovern admits: “I was thinking, ‘Well obviously that’s going to happen, but how will it affect the main audience?’

“You’re vicious as a writer,” he explains. “Hopefully you’re a sensitive man, but there’s a steel rod through you as well.”

There’s clearly great compassion alongside that steeliness, however, and McGovern can’t help but be affected by the stories he tells.

“You’re looking for energy as a writer, something to keep you going back to the typewriter. When you know it’s affecting real people, that gives you the energy.

“When I started to write the docudrama on Hillsborough [which aired in 1996], the kids I was writing about were dead, and I put their pictures all around me. Whenever I got tired, I saw a dead child and I just carried on.”

Born into a working class Catholic family, the fifth of nine children, McGovern had severe problems with speech as a child. I spent all my childhood listening, because I couldn’t speak. I just listened to people and watched them,” says the writer, who speaks with only the occasional hint of a stammer now.

After working at a number of semi-skilled jobs, he went back to college to train as a teacher, although he admits: “I was a good teacher for a year, but I taught for three - all my energy had gone by the second year. By the third year, I was a disgraceful teacher.”

He began writing plays for local theatres in Liverpool, and landed a writing gig on Channel 4 soap Brookside.

His big breakthrough came in 1993 with the ITV crime drama series Cracker, starring Robbie Coltrane, and he continued his gritty, realistic storytelling in shows such as Dockers, The Street and the International Emmy-winning Accused.

He and wife Eileen now live in the “posh part” of Liverpool (“I went further and further south as I got more and more successful”) and enjoy spending time with their four grandchildren.

“They’re ruined,” he says with a laugh. “They get what they want. I take them to Tesco and say, ‘If you get something educational, you can go up to 15 quid, but if it’s rubbish, you can only have seven quid’. Then they say, ‘Grandad, can I get something educational and something rubbish...?’”

Next up is a large-scale new BBC Two show Banished, a seven-part series about a group of convicts in 18th century Australia.

As for turning down ‘worthy’ stories from time to time, McGovern explains: “If everything you wrote was about injustice, you’d be a bore. I’m no saint.”

:: Common airs on BBC One on Sunday, July 6