THE message in the autograph book reads “We opened it, let’s hope we don’t close it... " There has never really been any danger of that.

Twenty-five years after The Blue Nile helped to open the Glasgow Royal Concert Hall, the venue is still going strong, staging some 300 concerts a year and continuing to attract the widest range of shows. A trend established even before its official opening on October 5, 1990, when the pre-launch attractions included Robert Buchanan & co, and Australian singer Jason Donovan, is still evident in 2015. On successive nights later this week, for example, the main stage will host Moscow Ballet La Classique performing Swan Lake, late-70s pop favourites Squeeze, the RSNO's Pictures at an Exhibition, and the World Famous Elvis Show.

The stage has of course hosted dozens of top international names over the years: Shirley Bassey, B.B. King, Jackson Browne, Bob Hope, Stephane Grappelli, Yehudi Menuhin, Montserrat Caballe, Jessye Norman, Cecilia Bartoli, the Berlin Philharmonic, the Vienna Philharmonic.

The hall has several employees who have been here since the very beginning. One of them is Karen Taylor. Her first job was in the box office. She became events manager at 23, "and I had to get into the big bad world of dealing with pop and rock promoters. That was a learning curve, working in a male-dominated industry. They all tend to be in the industry for a long time, so when someone new comes into it, you're tested." She recalls working with Elvis Costello's booking agent, Paul Fenn, "discussing such things as the hall rental, the ticket pricing. But it was really exciting - it's such a great industry to be in."

Karen is now Events and Commercial Development manager at Glasgow Life. As you talk to her, you get a sense of how the music business has changed over the last quarter of a century.

"I started in August 1990, when the hall was still being built," she says. "We were initially based across the road in what is now the Premier Inn; we could see from the windows that the hall's roof was going on, things like that. There was a mad rush to get into the building because these early gigs were already in the diary.

"When the hall was ready I was based in the box office, and it was a really exciting time, because in those days people queued up to buy tickets, and they paid with cash. There would be queues right down the street. I was the cashier, so I'd have all these £10 notes piled up on my desk. It was so busy. We were all very young, having just come out of college, or uni, or whatever. We had a great time.”

Prior to Bob Hope's appearance in 1994, Karen had to negotiate with Gleneagles Hotel (the only place Hope, a golf fiend, would stay) in order to get him the best room, and to get him a limousine to ferry him to Glasgow.

"I think the prestige of the building counted for a lot, back then,” she adds. “It was such a comfortable venue, too. I think there was a perception in the early days that it was probably quite posh - but you couldn't be quite posh and have Jason Donovan as your first concert. It still has a broad music appeal: it has never been seen purely as a classical-music venue. We've tried to broaden the programme, and the best element of that is Celtic Connections, which we started in 1994."

That festival came about after McNicol had spoken to BBC executives about getting more cultural activity into Glasgow in the dead month of January. "He was quite a character," says Karen. "He said to me and my colleagues, 'start a festival and make it about folk music'. So off we would go, and start a festival.

"It started very small, and in this building. I remember, in the early years, sitting on the phone, negotiating with Van Morrison's agent. That year's festival had already started. We were keen to get Van here for the next week, and I remember Cameron standing behind me, asking 'How are you getting on?'

"But we did it, and got Van here in seven days' time. We had to really market that gig in order to sell it out. There was a buzz when you got a big name like that."

She looks through the hefty autograph book, one of four in the hall's possession. The first page is signed by Princess Anne. Another signature, however, is an enigmatic squiggle, almost as if someone had been testing the pen. There are photos of Nelson Mandela, Princess Diana, and other household names. So many memories, a reminder of the role the venue has played in city life since 1990. Diana, recalls Karen, had a remarkable aura about her.

If there's one thing that Karen misses, however, it's the International Classical Seasons of old. Taittinger would be the sponsor, "and people would really make an effort and get dressed up. These nights were so glamorous, and it was great to be a duty manager then. There was one concert, the Vienna Phil with Sir Simon Rattle, when I was on duty. That was one of the nights of the year in the music calendar."

She believes the hall needs to improve the lustre of its international reputation and entice more world-leading orchestras back. Leafing through the autograph book she spots the signatures of by the Berlin Philharmonic Orchestra. "They were a big, big orchestra," she says. "It would be good to have something like that again."

Karen talks about the stars who love returning to the hall, about the venue's backstage facilities and the "really nice" dressing-rooms. One last memory surfaces: the ardent fans of one singer who would patiently queue for days to get tickets to see him. The star's name? Daniel O'Donnell.