'Their music is amazing, they're all gorgeous and Niall's really special to me'

It will be an hour, though, before Harry Styles and chums open the show at 1pm. To those waiting, the anticipation is physical in its effect. There is much pre-emptive squeaking and squealing and, when the five-piece band finally appear, they are greeted by an eruption of adulation. One Direction are The Beatles, Bay City Rollers or Take That of our time.

To an untrained observer it is not immediately apparent what the fuss is all about. Harry Styles, idol, receives the loudest cheers and plenty of young girls have his name written on their faces. A highly symmetrical young man, his plush hair is rollered almost double the height of his forehead and he is dressed casually in an over-sized green sweatshirt, jeans and trainers. He looks bored when not speaking. When speaking he twinkles and the girls near the front quiver.

"I love him," says Rebecca Harris. Her friends nod in agreement. "I'd do anything to meet him. Anything." I tell her about my friend Denise who bathed in fish guts in order to meet Paolo Nutini (it was a radio competition). She makes a face suggesting Denise is a rank amateur. The 16-year-old from Edinburgh has seen One D five times, in various places, and is leaving after the gig to go to Glasgow Airport where she hopes to spy Styles going for his plane. The group have broken off from their 60-date Where We Are tour to open BBC Radio 1's Big Weekend in Glasgow but once over, they are going straight to the airport to catch a flight to Ireland, where the tour continues. "If I had a credit card I would buy a ticket and get on the same flight, if it was a public flight. Can you imagine? Sitting next to Harry on a plane?" Rebecca adds. It seems the appeal is the fact that the gentleman would have nowhere to go.

Nearby there are fans wearing One Direction masks. Next to them, Charlotte French is bouncing on the balls of her feet, animated with excitement. She says she has been a fan of the band since they first appeared on The X Factor in 2010 and then signed to Simon Cowell's Syco label. Now 18, Charlotte's ardour shows no sign of abating. She has a tattoo of band-member Niall Horan on her ankle and a small One D tattoo on her wrist. She had them done when she was 15 but didn't tell her parents until recently. "I'm their biggest fan," she says. "I love them so much. Their music is amazing, they're all gorgeous and Niall's really special to me. I know if I could meet him I would be in with a chance with him but it's really hard to get close to them. Sometimes people will put on Twitter that they've seen them, like if they're in Glasgow, and I'll go there to see if I can see them. I dogged school twice. Once I read that Harry had eaten in a branch of Pizza Hut so I went and ate there."

The five young men comprising One D, Harry, Zayn Malik, Liam Payne, Niall and Louis Tomlinson, seem to appeal to all ages. Harry has had relationships with women many years older than him, while all five have boyish features that make them non-threatening to younger girls. Their single, Story Of My Life, was play-listed by both Radio 1 and Radio 2 - a sign of their dual appeal.

Cousins Charlotte Reid and Cerise Patterson - Niall and Harry fans, respectively - are at the Big Weekend thanks to the generosity of their mums. Eight-year-old Charlotte's mum, Deborah, said they had paid £200 a piece for tickets to ensure the girls saw their idols. "They have both liked One Direction from the start and it's cost us about £400 all in to come here today - a lot for 20 minutes," she said. "I don't really like them, but Charlotte loves them [Charlotte nods emphatically] so I'm willing to take one for the team. The girls were so happy to see One Direction live so it was worth it for them - though maybe not so much for me."

However, some older fans are as manic in their devotion as the younger ones. When rumour began that Pete Townsend was trying to have Best Song Ever banned due to its similarities with The Who's Baba O'Riley, thousands of fans took to Twitter to tell him where to go. The tweets were no-holds barred. "HOW DARE YOU... I'LL KILL UR FIRST BORN," for example. Townsend released a statement saying that he wouldn't, after all, dare.

Emma Robertson, 21, with her friend Aisling Carmody, 22, are dressed in their One Direction T-shirts for the occasion. Aisling, from Tullamore in Ireland, says she had cried - "just a little" - during a couple of songs. It was the first time both had seen the band live and they were impressed. "I wouldn't be a major fan," said Aisling, "But I do love them and now I can say I have seen them."

Sisters Aynsley and Claire McDowall have also been One Direction fans since the band formed. Having tried many times to get tickets for their live gigs, the pair have now finally seen them and were thoroughly impressed. Both said part of the appeal is the fact the boys are attractive to all ages. "I like the fact Harry likes an older woman," Aynsley, 26, says. Claire, a teacher, says her primary one class are often squabbling over who is going to be Harry Styles's girlfriend. The little ones were impressed that Claire was going to see them this weekend.

One Direction were the top-selling recording artists of 2013 while their third album, Midnight Memories, was the bestselling album of the year. The band's music seems to play a big role in their fans' lives. "It's not so much about the music," says one fan Aoife Malloy. "I mean, the music is good, but it's the way they sing it. When they sing Little Things you can imagine they're singing it to you. When I got my Niall tattoo on my back I had that song in my head and it helped with the pain.

"Thinking about them helps with the pain for a lot of things," the 16-year-old adds. "It's hard being a teenager now. You need something to take your focus away and make you feel good. I feel good when I listen to One Direction. If I could just meet them now I'd feel even better."