Image copyright PACEMAKER Image caption Glory day: David Trimble, Bono and John Hume pictured together on stage in Belfast in 1998

It was the night that produced the defining image of Northern Ireland's progress to peace.

To one side, the then Ulster Unionist leader David Trimble. On the other, the then SDLP leader John Hume.

The man in between, holding their hands aloft like triumphant prize fighters, was the world's biggest rock star - Bono.

The Concert for Yes, which took place on 18 May 1998 in front of about 2,000 schoolchildren, achieved its aim.

Three days later, Northern Ireland overwhelmingly endorsed the Good Friday Agreement in a referendum.

Tim Wheeler, lead singer of County Down band Ash, had a stage-side view of the historic moment - but his memories of the night are not quite so romantic.

Instead, he remembers putting together songs on the fly and loaning guitars and equipment to the biggest band on the planet.

"U2 just flew in before the whole thing and they didn't bring any of their gear, they had to use all our gear," Wheeler told BBC News NI's The Sunday News.

Image copyright PACEMAKER Image caption U2's The Edge on stage with Tim Wheeler, David Trimble, John Hume and Bono

He recalled how The Edge from U2 had borrowed a guitar belonging to Charlotte Hatherley, Ash's then lead guitarist.

"He was trying to figure out the controls. He was trying to get more of a louder kind of sound and he stepped on one of her pedals and it was too huge a jump - and he sort of jumped. It was pretty funny."

They may have been overshadowed by Bono et al, but it was Ash who did most of the on-stage heavy lifting on the night, delivering a 40-minute set and then performing a few hastily-arranged covers with U2.

At the time, the young Downpatrick band were riding an upsurge of rising hype and popularity - their debut album, 1977, was a critical and commercial success, buoyed by heavy radio rotations for singles such as Girl from Mars and Oh Yeah.

Image caption Charlotte Hatherley, Rick McMurray and Tim Wheeler from Ash in 2002

Wheeler and co were in the studio recording the follow-up when they got the call - would they like to get involved in a concert campaigning for a yes vote?

"It all came about within a few days as far as I remember. I think it was just looking quite dicey whether the yes campaign would succeed.

"I think it was maybe U2's management got in touch with our management a few days before. We were in the a studio in London and they were like: 'Can you make it over to Belfast in three days time?'

"It was very important for us to be involved. I think U2 felt they needed a Northern Ireland band to make the concert really work - it was great."

Wheeler, who was 21 at the time, added with a laugh: "U2 were a massive, worldwide, legendary band from the south and they needed some youngsters from the north - it was a really good pairing, I think."

The free concert for young people was envisioned as a last push to help get the yes vote over the line in the week of the referendum.

Image copyright Pacemaker Image caption Mo Mowlam, Northern Ireland Secretary in 1998, at the referendum count

While a huge turnout of Northern Ireland voters would comfortably vote the agreement through by 71% to 29%, the security of a "yes" vote was less certain beforehand.

Catholics were expected to strongly support the agreement, but the deal needed cross-community backing and a solid majority to go ahead.

As the Washington Post reported at the time, David Trimble had his concerns.

"Over 70% we're safe. Under 60%, we're in difficulties. In between, you've got to look carefully at turnout, geographical variations to try to get an idea if we've got a secure enough base to proceed."

Just three days and a couple of phone calls with Bono later, Ash were on stage at the concert in Belfast's Waterfront.

Image copyright bbc Image caption Ash on stage at The Brickyard, Carlisle

"Everything was last minute," said Wheeler.

"I remember being on the tour bus driving there the night before - I think we were put on a mobile phone with Bono, trying to figure out what songs we'd do together and how the show would go."

It was decided that Ash would play their own show, with U2 coming on at the end to do a few numbers with an assist from the local lads, including covers of The Beatles' Don't Let Me Down and John Lennon's Give Peace a Chance.

According to Wheeler, Bono was "brilliant" although he did throw him for a loop by calling for a Ben E King classic.

"Towards the end, Bono just turned round and said 'let's do Stand By Me'. He just pulled that out of thin air, no warning whatsoever.

"It's four very simple chords, we just started winging it and then he just looked at me and said: 'You sing the next verse'.

"I was like, I have no idea what the lyrics are at all, so I said 'you just do it'."

Despite these understandable hiccups, the concert was a major success and, of course, produced that iconic image.

Image copyright Ash Image caption Tim Wheeler says Belfast was "a very different place to grow up"

Wheeler remembered "a great feeling of positivity" after the concert that resonated with a band whose three founding members had lived all their lives under the shadow of the Troubles.

"Coming to Belfast always felt very edgy. The Army was everywhere, of course, and always bomb threats and incidents in our town.

"I do remember I was up in Belfast and saw a policeman had just been shot and was being covered in a body bag.

"Being children you just get on with it and think it's normal. And when we started travelling the world you realise it was a very different place to grow up."

Two decades on from that night, and the 1998 agreement referendum, devolved government in Northern Ireland is out of action.

It is a "very sad" situation, said Wheeler, but "at least we're living in a time that's a lot more peaceful".

Maybe another star-studded night at the Waterfront could help?

"I wonder! he said with a laugh. "Yeah, get it together - if a concert could work in a same way for that, we need to sit down and sort it out."

You can hear the full interview with Ash's Tim Wheeler on The Sunday News at 13:00 GMT on Sunday.