It’s not a life for the vaguely committed: the eight-hour round trips twice a week from Gaoth Dobhair in Donegal to Leinster House on some terrible roads; the soul-less hotels; the commitment to live on the average industrial wage; the clients who introduce themselves with the dreaded words, “there’s four votes in my house”.

Then there are the loathsome habits of rival politicians. Like the ones who phone hotels for a list of the wedding bookings so they can send congratulatory telegrams to people they have never met. Or attend every funeral in the constituency, known or not. Or make separate “representations” on behalf of every one of 80 people on a housing waiting list, when there are only 12 houses available .

Pearse Doherty tells these stories in a genuinely dismayed tone. “That is not politics,” he says. “It’s what in my view has led to all the destruction we’ve seen in the last few years.”

Sinn Féin’s finance spokesman, who topped the Donegal South-West poll with 33 per cent of the vote, is now one of the most recognisable faces in the country. Doherty’s is a self-taught financial mind. He always had a head for figures, he says – his first year maths teacher barely beat him in an algebra match – and he reads voraciously.

He is also a techie, and has more than 18,000 Twitter followers. His weekly meetings with Donegal Sinn Féin councillors are held via Skype. And he ensures those endless car journeys are never wasted by copying and pasting documents into an app called Speak It!. That way, he can listen to thrilling financial reports on the road.

Tragedy and opportunity

A remote area blessed with peace and natural beauty should be heaving with tourists. But half the businesses seem to have closed, including hotels sited almost on the shoreline.

We take a short tour that includes lovely Bunbeg harbour and the industrial estate that used to employ 2,000 people but now just 500. In there, Doherty points to a site bought by a group in 1966 – on the 50th anniversary of 1916 – and presented to Gaeltarra Éireann (predecessor of Údarás na Gaeltachta) on condition that it be used for job creation.

“It was a way of marking 1916 by enabling people to come home from Glasgow,” Doherty says, with obvious pride. Would he prefer that to next year’s martial set-pieces ? “Without a doubt. I would like to see it done again. 1916 needs to be about more than flying the flag and parades.”

But no tour of Gaoth Dobhair with Pearse Doherty would be complete without a stop at a monument, erected in 1954. It is to the memory of “Patrick O’Donnell from the parish of Gweedore who was put to death in Newgate Prison in London on 17 December 1883 because of his high loyalty to Ireland”.

O’Donnell was convicted of murdering James Carey, whose testimony for the prosecution led to the executions of five men adjudged responsible for the Phoenix Park Murders. On its unveiling, the local priest reportedly expressed disapproval of a monument commemorating a man who had committed murder.

We also pause outside Derrybeg church, where Doherty tells the story of a long-ago unscrupulous landlord who caused the church to be built over the river. As a result, many lives were lost in a flood.

These are the different sides of Pearse Doherty. One that is practical, thoughtful and forward-looking, and one that is always looking back, framing life through the filter of the Fenian dead.

He was born in Glasgow and might still be there but for the fact that an uncle suffered a catastrophic injury in a fall. The family were back in Donegal for the summer break when his grandmother asked them to stay.

He was three, and Ireland in 1980 was hardly the land of milk and honey. But young Pearse’s parents, Michael and Gráinne, were used to hardship. As children they had lived through the era of the hiring fairs. His mother was hardly nine when sent to work for another family.

When she and Michael emigrated to Glasgow in 1963, she worked on the buses collecting tickets while he laboured on construction sites. Their six children were born and reared in a one-bedroom house in a close. “And mum tells me they took in a lodger . . . ,” Doherty says with a wry laugh.

Seventeen years later, they were back in Gaoth Dobhair. “My uncle’s tragedy created its own opportunity,” he says now.

The six siblings still live within a kilometre of one another. Their father, who died suddenly three years ago at 71, is keenly missed. Doherty’s voice thickens as he talks about him.

“It changes you. That was my first real experience of losing someone very close. Everybody goes through it, but you never understand until it visits yourself.” Michael and Gráinne were soulmates, their son says, from the time she laid eyes on him in a dancehall in his diamond jumper.

‘I’m going to play my part’

He lives there with his wife, Róisín, a nurse who retrained online as a schoolteacher, and their four young sons, aged from nine down to three. Gráinne, now 72, lives behind them in a house built with credit union loans when there was no council house forthcoming.

Michael Doherty was a Fianna Fáil supporter who canvassed for Pat the Cope Gallagher. Grainne was a Fine Gael supporter. Both would have described themselves as “republicans”. However, Doherty makes careful distinction between his father’s brand of republicanism – with its origins in Michael’s father’s time in the old IRA, in the era of the Black and Tans – and the modern Troubles.

“He was very proud of that tradition,” Doherty says of his father. “It wasn’t that he would have seen himself as a republican in the context of the new Troubles.”

He is pretty sure that music had more impact on his politics than his family had. “The songs, Kevin Barry and all that stuff – I actually think that music plays a big part. Most people just sing the songs not knowing what they’re about, but I wanted to find out who was this ‘boy of 18 summers’ and why he did or didn’t do it and all the rest.”

Doherty was restless around 1989, during his early secondary school years: “I think I wanted to do something or find something. I didn’t know what it was.” He took out three books from the library, one on the Catholic church, one on John F Kennedy, and one on the history of the Northern Ireland conflict.

“It was a very dull book . . . but there was one wee bit about a person called Kieran Nugent, who in 1976 went into the H Block prisons and refused to wear his prison uniform. There was an asterisk after his name and in the footnotes it said that 10 people died on the subsequent hunger strike in 1981, including Bobby Sands MP and Kieran Doherty TD, and I wanted to know what went on there”.

So he talked to a butcher where he worked part-time, and this butcher was in college and said he knew about the Sinn Féin shop in Parnell Square in Dublin and arrived back with the Sands autobiography and a copy of An Phoblacht.

Appetite whetted, Doherty phoned a friend in Glasgow. “I remember saying, ‘This is still going on’ [in an amazed voice] and ‘I’m going to play my part’. That got me into republicanism. Then I deepened all that, and was looking at our family circumstances and that we couldn’t get a council house.”

He pauses: “So maybe the republicanism was a more romantic idea and then grew into something that was a lot more, that – yeah – had a socialist edge to it. But I call it just fairness. It’s about fair play.”

Upset parents

They were upset, he says, when they heard he had been spotted on the news holding a tricolour and talking to Martin McGuinness at a Bloody Sunday rally in Derry. By now, he was selling An Phoblacht in the pub and maintaining a billboard at the top of the road calling for the release of political prisoners.

“People used to paint over it, burn it, knock it down,” he says. “And every time that happened, I’d erect it again before I’d go to school. I put it up in concrete then.”

At 15, he applied to join Sinn Féin but the only Donegal branch was in Letterkenny, 32 miles away, making it inaccessible.

He didn’t do a good Leaving Cert. “I knew I’d have enough points for what I wanted to do – civil engineering.” Was that really what he wanted ? “No, it wasn’t,” he says, with a big, incredulous laugh. “A few others in the class wanted to do it.”

Two years into the DIT three-year degree course, Doherty claims they were encouraged by a lecturer to get out and gain experience while there was a shortage of engineers and then come back. “So I went out and never came back.”

Famously, he called himself a civil engineer, as opposed to technician, in webpage biographies, which triggered a minor eruption a few years ago. The biographies were clarified. He says now that he did a couple of months in Letterkenny IT in 2002 with a view to completing the degree. But a general election put paid to that.

In the meantime, he was putting his technician’s training into practice around bustling Dublin building sites, such as the Four Seasons and Wheatfield Prison.

The phone call that changed his life came from Pat Doherty, a well-known Sinn Féin (also born in Glasgow) and abstentionist Westminster MP once named under parliamentary privilege as a member of the IRA army council. “It was one of those moments where you remember exactly where you were,” Doherty says.

Out of that call came a commitment to go home with the task of helping to build Sinn Féin, parish by parish. Doherty’s income up to 2004, he says, came from work on an ex-prisoners’ project in Letterkenny. The payment of €17,000 that came with his council election allowed him to work full-time in politics.

The DIT years featured other fateful encounters. These included Matt Carthy, now the Sinn Féin MEP for the Midlands-North-West, with whom he set up Sinn Féin Republican Youth. And it was Carthy who set him up on a date – actually the unveiling of a monument to the hunger strikers in Monaghan – with his future wife, Róisín, from Iniskeane, Co Cork.

My ‘only dark secret’

Doherty’s only dark secret, he said once, is that he used to be a fan of heavy metal. He is perceived as a Sinn Féiner without baggage. Yet in pride of place on his office wall in Bunbeg is a framed copy of a famous Bobby Sands poem, The Rhythm of Time: “There’s an inner thing in every man . . . It is ‘the undauntable thought’, my friend/That thought that says ‘I’m right!’”.The poem come with an image of gunmen firing shots over Sands’s coffin.

“I am who I am,” Doherty says. “I believe in what I believe in. I’m not going to change my beliefs to suit anybody else. Fair play is what makes me tick. I know that’s broad stuff, but I also believe strongly in the reunification of our country.

“I’m a republican. Every Easter, I go out and remember those men and women who gave their lives for Irish freedom, and they go right up to the present day. Some people say, ‘oh you have baggage because . . . members of the IRA were supportive of Sinn Féin or some were in Sinn Féin. That is fact. I’m not going to deny that or deny myself.

“If people say, ‘well, I don’t like that part’, it’s up to me to convince them.”

But what about the continuing dark cloud that hangs over the party: Jean McConville, the disappeared, the vile murder of innocents? “Hand on heart, I’m only asked about that by journalists,” he says. “There’s things that happened in the war in the North that were completely unjustifiable, absolutely. Nobody could stand over them. Equally, things that happened in the Tan war – the talk about the old IRA who secretly buried people.”

Yes, but the difference is that he knowingly joined a party with such links.

“I joined a party that believes in Irish unity, that believes in bringing this about. I remember one of the documents I read, Pathways to Peace, which talks about taking away the causes of conflict. The IRA was a symptom of conflict.”

He loves Bobby Sands, who died when Doherty was four, and he loves that Bobby Sands image on the wall. “It’s there in a prominent position because when people come in here to talk to me about whatever, what you see is what you get. That’s part of our history.

As for the Maíria Cahill allegations, he takes refuge in the fact that her case was tried in a court of law and insists that “there are no dossiers in terms of covering up sexual abuse. They don’t exist. I’m an officer on the ardchomhairle and the officer board of the party, and it doesn’t exist.”

Which of course proves nothing.

In any event, Doherty says it’s not his job to justify what happened in the IRA. People have seen these allegations “dragged out over many years in numerous television programmes and interviews, and that despite all that, more and more people decide to join and support our party”.

The Adams factor

“Yeah,” Doherty says with a keen edge of sarcasm. “Those people who wish for our support to rise and rise and try to advise us time and again that if Gerry Adams were moved aside, then we would continue to reach new dizzy heights?

“These are the people who were saying that before the last election, when Sinn Féin secured 19 and a half per cent under the leadership of Gerry Adams. You cannot have it both ways – when we double our vote, you can’t say that has nothing to do with Gerry Adams.” And yet, support in the polls seems to be plateauing at 18 per cent. “I’ll tell you something: if we achieve 18 per cent in the next general election, it would be an amazing feat for a party to increase their vote by 8 per cent”.

Doherty is under no illusion about the role of republicanism is Sinn Féin support.

“I don’t think people are going to vote for me because they want an end to partition in Ireland. A certain proportion do, but it’s not their burning question. What we have to do as a party is convince people it is in their best interest in terms of a united Ireland.”

Meanwhile, the creature to which he and the others on the banking enquiry committee have given so much of their lives, was grinding towards its summer break. Was it worth it all?

“The honest answer is, I don’t know,” he says. “I think for the public, they wanted to see the faces of the leaders, the bankers, the politicians, the developers and see them up front. I always thought that was the best outcome about the enquiry.”

The frustrating part, he says, is that the committee members are like a trial jury, barred from talking about anything that comes under the enquiry’s terms. “But for all its limitations, I think it was the right thing to do. There was always going to be just one shot.”

By the time this appears, Doherty and the family will be on a camping holiday in France. His phone will be switched off and he will not be attending to the news.