Charles Haughey, I presume?

Patrick Malahide's performance as a disgraced Irish politician caused an uproar in Dublin. With the play about to open in London, the actor speaks to Daniel Rosenthal

If you had to choose just one play to illustrate the subjectivity of audience reaction, you would need to look no further than Sebastian Barry's latest drama, Hinterland.

When Patrick Malahide was offered the play's vast leading role as Johnny Silvester, a disgraced former Irish Taoiseach awaiting the verdict of a corruption investigation, he read the script and immediately told the director, Max Stafford-Clark: "This is Macbeth, King Lear and All the President's Men rolled into one." He also noted that Silvester was "obviously loosely based on Charles Haughey, in that the public events in the play are clearly public events to do with contemporary Irish politics. But I could see immediately that this wasn't a piece of journalism. It's a synthesis of the public life of Ireland and, in a way, the private life of Sebastian Barry, who has written a series of plays about family [including The Steward of Christendom and Our Lady of Sligo]. Here he's tackling the figure of the father, and has taken this great imaginative leap by making him the father of the nation."

When Hinterland had its first performances in Bolton in January, Malahide says that English theatre-goers, "who don't carry lots of baggage about Haughey, responded to it as a play about power, fatherhood, sex". Then Stafford-Clark's production moved to the Abbey Theatre in Dublin, where for years the public and media have devoured and debated every detail of Haughey's investigation by an anti-corruption tribunal. "Suddenly," says Malahide, "we became a piece of news rather than a piece of theatre."

Irish critics unanimously agreed that Silvester was simply Haughey by another name, and itemised the two men's common traits, from pomposity and infidelity to a taste in expensive shirts. Haughey dispatched a member of his legal team to the Abbey, and there were reports that his family were seeking an injunction against the production. "We were all surprised at the extent of the reaction," Malahide says. "The unfortunate thing was that some people, particularly in the Dublin press, criticised the play as a piece of journalism, rather than as a dramatic metaphor. They said one character was 'badly researched' just because the man he is based on wasn't bald in real life. We were on this loop of negative criticism, which is very difficult to step off." Bearing in mind the riots that greeted Synge's The Playboy of the Western World at the Abbey in 1907, things could have been worse. "I sent an e-mail to a friend saying 'We're getting a very strong reaction.' He replied: 'Until you hear small arms fire in the stalls, don't worry.' But it'll be a relief to get to the Cottesloe this week. It will be like doing a completely different play."

Even those Irish critics who damned Hinterland were, much to Malahide's surprise, unanimous in their praise for the precision with which he had captured Haughey's voice and mannerisms. He is a gifted mimic when occasion demands, and cricket-lovers like me still cherish his spot-on Geoffrey Boycott in Our Geoff, a fine 1980s television play. Yet he says,"One of the first decisions I took was that I wasn't going to do a Rory Bremner [with Haughey/Silvester], because that might cheapen the play. But I thought it would be crazy not look at a couple of videos of Haughey. I thought, 'OK, that's what he looks and sounds like, and we'll leave it at that.' But the flavour I've brought to it was enough to make the audience completely identify me as Haughey. Some of it is complete accident. In Dublin last Saturday, somebody who knew Haughey very well told me, 'That moment when you stand waving at the window is pure Charlie.' Well, I couldn't possibly have known that – it just seemed the right thing to do at that point in the play."

Irish coverage of his performance also dwelt on a question of national identity: is Malahide English or Irish? He was born in Pangbourne in 1948, lives in north London, speaks with an received-pronunciation English accent and spent years in provincial rep (Manchester, Birmingham, Sheffield, Bristol). His "rather severe features" (his own description) are familiar to millions, thanks to memorable performances in a string of distinctively English television parts, from hapless Detective Inspector Chisholm in Minder, to his triple role in The Singing Detective, dry-as-dust Casaubon in Middlemarch and finely tailored sleuthing as Inspector Alleyn.

On the other hand, his parents were working-class Irish Catholics who worked "incredibly hard" to pay for his education at Douai, a boarding school in Reading run by Benedictine monks. Before Hinterland he had shown an affinity for Irish and Ulster characters in films such as December Bride and A Man of No Importance (as an officious Dublin tram inspector).

"The first Irish reports on Hinterland said I was English," he notes, wryly. "Then other papers immediately went, 'No, he's Irish.' It was quite interesting to be fought over, and I didn't mind, because I've always been proud to call myself Irish. That's a very conscious decision, because at school I was immediately made to feel that Irish Catholics were in a minority in the wider community, and looked down upon. Some react to that experience by eradicating their own Irishness – as half my own family have done. Others, like me, fiercely maintain it."

Playing Haughey has therefore come more naturally than his last appearance in a new play (also at the Cottesloe), as Edmund Spenser in Mutabilitie (1997), Frank McGuinness's rather muddled drama about the poet's traumatic stint as Sheriff of Cork in the 1590s. "It was very odd," he said at the time, "to feel Irish and be surrounded by Irish actors, while playing this epitome and icon of English imperialism."

Where his uncharacteristically hesitant performance in Mutabilitie suggested an actor ill at ease with an underdeveloped character, his Hinterland experience is rekindling an enthusiasm for new writing previously generated by his work in plays by William Nicholson, GF Newman and Nick Dear. "With new plays you're blazing a new trail, which is more interesting than the prospect of playing Claudius or another of the Shakespeare parts that I've frequently been offered."

His own writing for television, crafting thrillers and dramas as PC Duggan (his real name, changed when he found that Equity already had a Patrick Duggan), has increased his admiration for Sebastian Barry's dedication and flexibility. "He had been working on Hinterland with Max for two years and was on his 11th draft before I read the play. It's normally quite difficult to have the writer in rehearsals, because actors need to make quite brutal editorial responses to things they feel aren't working, but Sebastian has been gentle and gracious and taken it all with great good will."

He is equally complimentary about Stafford-Clark's rigour and finesse, while suspecting that their partnership may be jinxed in one respect. "The only other time I've worked with Max was on GF Newman's One Bad Apple 20 years ago, which was about corruption in the Metropolitan Police. There were barristers and policemen in the audience and talk of injunctions. Every time I work with Max, somebody threatens to close down the play."

'Hinterland' previews from tomorrow and opens on Monday at the Cottesloe, SE1 (020-7452 3000)