Negotiating with people who were almost “mortal enemies” was the only way to deliver the Good Friday Agreement, a former Ulster Unionist leader has said.

Lord Reg Empey, a close ally of David Trimble, said many people are alive today because of the historic peace agreement the politician helped to negotiate in 1998.

Lord Empey spoke to the PA news agency about the tensions within unionism over the agreement in an interview to mark its 25th anniversary.

The Ulster Unionists, then led by Mr Trimble, was the largest political party in Northern Ireland in 1998 but was split by his support for the deal and was eventually overtaken as the dominant force in unionism by the DUP, which had remained outside the negotiations.

Lord Empey said that much of the “spadework” for the agreement had been done in previous years but given new impetus in 1997 when Tony Blair became prime minister and Bertie Ahern became taoiseach.

However, he said tensions grew within the UUP as the negotiations moved towards a deal just before Easter the following year.

He said: “There were people who didn’t even want to be in the talks because of the presence in them of Sinn Fein, who at that time were wholly supporting the Provisional IRA.

“But I had been in local government for many years and Sinn Fein councillors were there. By the time we got to the talks I had 10 or 12 years of experience of working with them at local government level.”

He added: “Of course it was difficult, I was a member of the Police Authority at that time and I saw what the Provisional IRA was capable of doing.

“I have to say that it was, in my view, the work and sacrifice of the security services over many years that had brought the Provisional IRA to the point that it was at in the mid-1990s.

“It was full of informers, it had been ground down and the only thing that had really kept them going was Colonel Gadaffi’s Semtex.

“Without that they would have had very little in the way of firepower.”

Lord Empey said the only alternative to the negotiations was further violence.

“There were tensions, naturally. How could there not be?

“But you have to decide, do you stay in the rut that you are in, within parameters that are chosen for you by others, or do you try and break out of that and look at the bigger picture to get a longer-term solution which will allow the community to become more normal?

“People were angry. And why wouldn’t you be angry? It was difficult to withstand that because we had to negotiate with people who were almost mortal enemies.

“It was difficult and people found it really, really hard. It was a big moral issue for people but if you look at peace processes around the world, they generally end up with that type of negotiation.

“If politics was seen not to work then the alternative at that time was paramilitarism.”

Other parts of the 1998 deal which proved to be controversial were the release of paramilitary prisoners and the reform of the RoyalUlster Constabulary.

Regarding the prisoner release, Lord Empey said: “It was dreadful. Mo Mowlam did it in the middle of the referendum campaign which I think maybe cost 5% of the vote. I think we could have got an even higher figure.

“The police reforms were obviously also hugely problematical as well but we concluded that the Government was going to do the police reforms and come to some sort of deal over prisoners whether or not there was any agreement involving politicians.

“In those circumstances we concluded we would have lost the constitutional gains, such as the principle of consent, such as getting the Irish constitution changed, and still had prisoner releases and still had reform of the police.

“It was a very difficult time and bearing in mind many of our members, including elected members, had been murdered by the IRA and many more had been attacked; this was not easy stuff.”

Lord Empey said the peace deal is much more highly regarded around the world than it is in Northern Ireland.

He added: “Whatever the flaws in the agreement, and there are many, I console myself with the fact that there are so many more people in Northern Ireland alive today who, in my opinion, would have been in their graves had we not got an agreement.

“We have now one, and moving on to two, generations who have grown up who know nothing about the Troubles. You have to be well into your late-40s to have any significant memory of what was happening here in the 1970 and 1980s.

“In many ways that is a success and it is highly regarded internationally. It is regarded as a template for how conflicts might be ended.

“There are two sides to the story and I can see both of them

“We were the generation which had actually gone through the Troubles, and unless you have seen that and heard that and experienced that, it is very hard to put it into a context.

“I suppose when you stand back from it, in terms of life and death and injury, it has contributed to avoiding a lot of that and that must be your top priority.”