"When the music starts please don't surge forward, McFly don't want you to get hurt. Anyone crowd-surfing will be evicted. And if it gets too loud ask a member of staff for some earplugs."

The announcement came before McFly hit the stage for their sell-out St George's Hall gig this week. It was the first concert I'd been to where the crowd was given instructions, it felt like being on a school trip.

I was reminded of a Steps concert I'd heard about where the words Anyone who wants to go the toilet, go now' flashed up on a screen before the show started. Rock 'n' roll.

As I looked around at the mass of giddy teenagers packing out St George's Hall - and the rows of children sitting with mums - it struck me how much pop concerts have changed over recent years.

There was a time, not too long ago, when you reached the respectable age of 15 or 16 before you went to your first gig. It was a rite of passage, like your first kiss, your first bra, or your first swig of lager and black.

Pop music was exclusive to teens. You never forgot your first single, bought round about the age of 12 or 13 with your Saturday job earnings - mine was Visage's Fade to Grey, I was bitterly disappointed it didn't come in a picture sleeve - and you looked forward to the time when you could see bands live on stage.

It seemed an eternity but when you finally got there it was like joining an exclusive club. The under-12s were left with their noses pressed against the window.

Now tots as young as five are at gigs. Pop music has become more tweenie than teeny. Somewhere along the line, probably in the Eighties when the dreadful Mini Pops took off, record industry execs woke up to the "ker-ching!" of the pre-teen market. So began the packaging of inoffensive, disposable, child-friendly pop. Bands were created in labs by people like Pete Waterman and chart music saturated Saturday morning children's TV. Then came the concerts - huge corporate affairs in out-of-town stadiums. Pop music became child-friendly and bands like Steps, S Club 7 and even the Spice Girls were churned out to meet the market.

There's nothing wrong with children grooving to bubblegum pop, or even proper music if their parents introduce them to decent stuff from an early age, but since I grew up at a time when children were neither seen nor heard at rock concerts I can't get used to the idea that five-year-olds are being initiated into the club I waited until I was 16 to join.

It hit home when I took my eight-year-old niece along to this week's McFly gig. After several e-mails and phone calls I managed to get two press tickets, as I was writing a review for the paper. Since I'm about a quarter of a century too old for the pop rockers I needed to take a tweenie', so I borrowed Eleanor.

When I arrived to collect her she was deciding whether to wear pumps or boots. As she raced downstairs in her pink and black stripey top and black leggings, a hint of lip gloss lighting up her face, I felt a lump in my throat. It didn't seem two minutes since I was taking her to see Postman Pat and here she was, dressing up for her first pop concert.

I was concerned she might be overwhelmed by the noise and energy of a gig. Thankfully we were in the dress circle, so I didn't have to worry about her getting squashed in the moshpit below.

I felt old and invisible as I surveyed the over-excited adolescents and pre-teens in their skinny jeans and crop tops, their hair straightened to within an inch of its life, taking mobile phone snaps of each other holding up McFly programmes (a tenner each).

Eleanor's eyes widened at the sight of the burly security men standing like Buddhas by the stage. One of them was handing a cup of water to a girl wearing flashing bunny ears, clearly feeling the effects of standing around for several hours. Ten minutes later Eleanor nudged me; another girl was being carried out, overwhelmed with heat and excitement.

A couple of girls behind us had been outside the stage door at 10am. "It started snowing but we didn't want to leave in case they turned up," said one. When did they turn up? "I don't know, we went to KFC."

I'd passed the stage door earlier that day and met a frozen group of diehard fans huddled together. Some of them had been there since 7am and appeared to be turning slowly blue. I admired their dedication - if you can't do something that daft when you're a teenager when can you? - and hoped the McFly boys would sign autographs on their way in.

The Bradford gig launched McFly's Up Close and Personal tour, covering the smaller venues the band doesn't normally reach. "We went for towns without arenas," singer Tom Fletcher told me during a recent phone interview. "Not everyone can afford to travel a couple of hours to their nearest arena. We thought there'd be fans out there who haven't had chance to see us yet."

It paid off, with a sell-out crowd clearly delighted to have the boys on their doorstep. And the band enjoyed the intimacy and connection with their fans.

When Danny Jones threw his water bottle out there was a mad scramble for it in the middle of the stalls. If he'd done that in a stadium it wouldn't have even reached the front row.

There was a bit of corporate till-ringing when Tom trotted out mobile numbers so the crowd could text download the new single - "Only the McFly Army can get us to Number One! Check permission if it's not your phone" - but overall there was a happy, intimate feel to the gig.

The support act was Lil' Chris from Channel 4's Rock School. With his baseball cap turned back-to-front, he looked about 12 years old but, bless him, he worked that stage.

"This one's called Getting Enough. Are you getting enough?" he screamed, rather inappropriately, at the crowd. The tweenies shrieked. I resisted the urge to tut.

"How cute was Lil' Chris? He rocked!" said a girl with too much eye-liner on who was holding court in the ladies' loos. The general consensus appeared to be that Lil' Chris was pretty cool.

It occurred to me that when I was a teenager I wouldn't have found anyone younger than me remotely cool. Pop stars had to be older than you so you could imagine being married to them. When I was 13 Simon Le Bon was 24. It could have been the perfect match.

I didn't actually get to see Duran Duran live until I was in my thirties, when they re-formed. I'd gone off Simon by then.

I missed out on Duran Duran first time round because my mum decided I was too young for pop concerts. I wasn't allowed near a gig until I was well into my teens.

So, if I'm honest, I was a bit resentful of the youngsters screaming their hearts out at Tom, Danny, Dougie and Harry on Tuesday evening. I had to pay my dues and wait patiently until I was 16 before I went to my first gig. It was a po-faced performance by Orchestral Manoeuvres in the Dark but it was such a momentous occasion in my life I remember every minute of it. I even remember the boy dressed like an extra from Brideshead Revisited who chatted me up.

Will the under-tens who screamed along to McFly's teen angst lyrics remember it forever? As Eleanor waved her McFly poster around to 5 Colours In Her Hair, I hoped she'd remember the first time she saw a boyband live. It's quite something in a girl's life.

But although part of me is envious of the kids who have it all too soon, I'm glad I'm not growing up in the download generation. My copy of Fade to Grey may not have come in a picture sleeve back in 1980, but I treasured that 7-inch single and I've still got it today. What will the kids who are text downloading their singles be left with in 25 years' time?