It was a call none of them had been expecting. Their friend, bandmate and brother, Stephen Gately, 33, had been found dead at his home in Port d’Andratx, Majorca, following a pulmonary oedema resulting from an undiagnosed heart condition.

It’s been four years since his sudden death, but it’s clear when I speak with Boyzone’s Mikey Graham, Stephen is still in the band’s thoughts.

“Even now it sounds weird when we say there’s four of us. We should be five,” says Mikey, his strong Dublin accent tinged with sadness.

“For a while after his death we were all emotionally unstable. Losing Stephen was difficult. It was sudden, it came from nowhere. So, we weren’t sure what to do with the shape Boyzone was in at the time.

“Some of us have said we regret doing the Brother tour and album, but we only regret it in so much as we were struggling to cope with our grief. The album and tour were already on the cards, we didn’t know what else to do, but keep on keeping on.

“It was a very emotional time. There’d be times when it would just hit you like a ton of bricks.

“You’d get used to talking about it, but then, at other moments it would stab you in the heart.”

Their bond with Stephen was strong.

Following news of his death, the band flew out to Majorca to bring back his body, and spent the night before his funeral at St Laurence O’Toole Church in Dublin, sleeping on the floor in sleeping bags, exchanging stories and remembering Stephen.

One of the two lead singers of the group, it was testament to his popularity that celebrities and fans from across the globe gathered at the service to pay tribute, united in their grief for the late heartthrob, who had been taken so unexpectedly from them.

“You know, we would never be able to replace him, it would be too difficult, too weird. We have 20 years of history together. For someone to come in...” his voice trails off, “it would be strange. You can’t just erase someone like that. They wouldn’t be able to just fit in.

“Stephen’s presence is always with us, he’s always there. We’ve just had to become more familiar with the shape of the band as a four.”

One of the most successful boybands of all time, Boyzone burst onto the music scene in the ‘90s, capturing the hearts of teenage girls and housewives alike, following their now infamous performance on Ireland’s biggest television show: The Late Late Show. Twenty five million record sales, four number one studio albums, six number one singles later, and in spite of Stephen’s untimely passing, Boyzone are still going strong.

In fact, they’re set to embark upon a new stage in their career with a major 18-date UK and Ireland arena tour and the release of a brand new studio album BZ20.

“It’s funny to think we’ve been together for 20 years. At the time we didn’t look beyond the day or week we were in, hence the name Boyzone.

“I wasn’t in the band when the name was chosen, but if I had been, I might have had a thing or two to say,” Mikey, 41, chuckles. “I mean, we’re not really boys now are we, we’re men! But hey, what’s in a name?

“After Stephen passed away we had no idea what the future held for us, if we were even going to continue as a band. But we were all left wondering what else could we really do? Of course I did Dancing on Ice and Keith did Coronation Street, Ronan was still singing...as was Shane...

“But we like being together, travelling together.

“This is a new phase for Boyzone. I like to think we’ve got a more grown-up, mature sound, which shows our progression through the years. We’ve certainly calmed down on tour, the most exciting thing you’ll find on our rider is a kettle and some teabags.

“It’s taken a couple of years, but we’ve begun to find our feet again. It’s the beginning of the next stage, we’re looking forward to the rest of our careers.”

l Boyzone will perform at the 02, Peninsula Square, SE10, on December 20. Details: 020 8463 2000, theo2.co.uk