Is it too much to expect an audience at a live show to behave like civilised human beings?

Judging by the behaviour of the young women in front of me at Sunday’s Diversity show, it would seem so.

The show was a sell-out and a lively crowd was delighted to see the Britain’s Got Talent winners in action. I was reviewing it – already a challenge as I was up in the grand tier, right at the top of St George’s Hall, and could only see half the stage. It didn’t help that three girls on the row in front insisted on standing up and filming the entire show on their mobile phones. All I could see were the illuminated screens of phones on outstretched arms.

When someone nearby politely asked them to lower their phones, as they were obscuring the view for several people, one of them unleashed a mouthful of abuse. I looked around and realised that mobiles were being brandished all over the auditorium. It seemed a little sad that people couldn’t enjoy a concert without trying to capture it on their wretched phones. It has become commonplace to wave them around at concerts, with no regard for others in the audience, and it cheapens the experience of live theatre.

I wondered what on earth they’d do with the footage afterwards? Surely boring your mates with grainy images of a concert is the equivalent of travel bores inviting neighbours round to endure their holiday slides?

What has happened to the basic good manners expected of audiences at theatres and cinemas? I was at the Alhambra recently, sitting behind a row of teenagers who were well-behaved apart from a lad on the end scoffing his way loudly through a bag of sweets and a giant chocolate bar and swigging from a bottle. His slurping, finger-licking, belching and packet-rustling was a constant distraction and, just when I thought it had finally come to an end, he produced a packet of chewing gum and chomped on that. It was like he was at home watching telly.

The day before, I’d been in a cinema where a group of youngsters spent an hour chucking sweets and racing up and down the steps. They were eventually frogmarched out by a security guard, but by then I’d missed chunks of the movie. The texting that was going on all over the place – irritating little pools of light peppering the darkness – was just as distracting. We have become a society of techno-obsessed philistines who lack basic manners and have the attention span of a toddler. Civilisation is on its way out.