Outside, Des Long’s modest three-bedroom midterrace house in a Limerick suburb gives no clue of his past life as a founding member of the Provisional IRA.

Inside, however, it is a different story. Long’s republican background is proudly revealed in his front room, with bookcases stacked from floor to ceiling with volumes on “the cause”.

This week Long was introduced to a new generation, many born after the Troubles were said to have been ended by the Belfast Agreement, on BBC’s Spotlight on the Troubles: A Secret History.

In the documentary, the Limerick man said he had sat across the table from Gerry Adams at IRA army council meetings, despite Adams’s denials that he was ever a member of the paramilitary organisation.

Long is no longer involved in paramilitary actions, but he supports those who are.

“I do. I’d be telling lies if I said I supported anything else. There’s been a number of operations in the past couple of weeks, so there are still people at it.

“As long as there are British soldiers in Ireland there’ll be people who would oppose them militarily. You can’t just say ‘Please leave our country’ – that doesn’t work. I feel you wouldn’t be going any place without a military campaign,” he says.

Des Long at home in Limerick: ‘They Brits may not be parading around in the streets, but they are here.’ Photograph: Eamon Ward

Forty years on, he insists the British cannot be trusted.

“You can talk to the Brits until you are blue in the face,” he says. “They’ll keep you talking and going around in circles.”

One can “talk”, he says, but, “don’t have a truce”.

Twenty years on from the Belfast Agreement, in the run-up to Brexit, Long knows he is in a minority. He does not care.

“Fight and talk. When people read this, they’ll think I’m mad,” he says, with a shrug of his shoulders.

British army watchtowers, once a feature of the Northern Irish landscape during the Troubles, can return at any stage, he says.

“They can be put up [again]. The Brits are still in our country.

“They may not be parading around in the streets, but they are here. They can get plane-loads of them over in hours.”

“It’d be grand if the Brits [declared] in the morning, ‘We are going.’ I’d say, ‘Thanks be to God, no more killing, shooting, and people [can] go home and sleep in their beds.’ But I don’t see [them leaving]. The Brits never left any place until they were driven out. That’s history.”

In 1969 Long and others split from the Official IRA, forming a provisional army council during a meeting at a house in Victor Fagg’s house in Athlone, Co Westmeath.

For 17 years, he was general secretary of the IRA executive.

“I must be the longest ever,” he says.

Later he was on the ardchomhairle of Sinn Féin, and on the National H-Block Committee.

He split from Sinn Féin and Gerry Adams in 1986 – opposed to the party leadership’s initial attempts to persuade the IRA to give up its guns – to join Republican Sinn Féin.

However, he left this group, too, in 2000 after differences emerged.

Adams denials

Adams's denials infuriate Long, who bangs the table with his fist to show his feelings.By denying IRA membership, Adams "betrays" every IRA volunteer who fought for a united Ireland, Long argues.

He looks distressed when he produces a newspaper article from 2013, with the headline ‘Those killed by IRA were murdered, says Adams’.

“It angers me, because it was a betrayal of [IRA members]. There is a fella I know that did 26 years in jail in England. He was betrayed. Another lad had an arm and leg blown off in England– a lad that went on an act of service and got blown up. They were all reading [Adams’s] statement.”

He hopes he will witness a united Ireland: “I’m hoping it will happen in my lifetime, although I’m pushing on now. I’ll be 80 next May, if I live that long, unless somebody . . . Nobody wants to die, but sure we all have to die eventually.”

He does not know, he says, if a united Ireland will come.

“I never thought it would be easy.”

However, old beliefs will not be abandoned now. “I’ll be a republican until the day I die. Whether people want me or not is another thing.”