The mission of every major television controller is to find programmes – such as "Doctor Who", "The X Factor" and "Strictly Come Dancing" – which cross generations and bring families together in a shared living room experience.
It doesn't work that way in radio. That's a medium in which audiences are segregated according to age, with each generation apparently unable to comprehend the musical tastes or on-air banter enjoyed by their parents or their children.
At least that's the philosophy of the popular music stations, which seem determined to rid themselves of their most popular presenters in order to remain cool with the kids. So Chris Moyles, 38, quit the breakfast show at Radio 1 last week and gave way to Nick Grimshaw, who is 11 years his junior. Moyles had spent eight years building an audience of more than 7m but the switch is intended to deliver a "new generation of listeners", says Ben Cooper, the network's controller.
Johnny Vaughan parted company with Capital Radio in November. Like Moyles he had been on the station for eight years and had been successful – hosting the most popular commercial breakfast show in London.
In another era, when radio presenters were only identifiable by voice, Vaughan might have lasted a bit longer at Capital. Chris Tarrant was 57 when he finally quit the network's breakfast show to make way for Vaughan in 2004. But in an era where presenters have to be highly visible – the face of the network – he says he couldn't get away with it. "We have to be honest with each other. You know, I'm a 45-year-old man. I am no longer simply a face for radio," he says, recalling an era when listeners were shocked to see honey-voiced DJs appear "on 'Top of the Pops' and they didn't look like Maurice Gibb – super handsome with big teeth."
Vaughan says: "Now it's much more about your image. Capital sell with TV ads and the fact is that I can't be the 'Face of Hit Music'. It becomes, after a while, like watching your dad dance. I could still dance at a wedding and that's kind of fine. But I wouldn't go clubbing with the kids. And that's what Capital is about."
He has decamped to Absolute Radio, which seeks an older demographic. It's a station that uses the expression "Faces for Radio" to emphasise the authority of its presenters – from Frank Skinner to Ronnie Wood – who have already established themselves as comedians, musicians or television presenters. Vaughan is off to hang out with the dancing dads. "I'm moving to a crowd where your face fits and where it's not so embarrassing to see you rocking out."
The switch to Absolute means that Vaughan will be moving out of breakfast into drive time, with a daily show through the Olympics presented from Hyde Park with Australian co-host Tiffany Cherry. "We will be looking back at what's happened that day and looking forward to what's happening in the night, it's a perfect time really to engage and entertain," he says. "I see it as being the Olympic drive time and I say that because if you put the word Olympic in front of anything you wouldn't normally watch or listen to, suddenly it's engaging. Badminton you don't bother, but Olympic Badminton?"
He is not certain whether it will lead to him becoming a permanent fixture in the Absolute schedule. "If it's enjoyable for them and me then you see what happens don't you?"
Vaughan is reluctant to talk about his time at Capital but then relents. "The thing is I used to really enjoy doing it and I do miss it terribly. I miss having something to go off and do every day and having that feedback from listeners. I'm quite institutionalised and there was an institution there."
Chris Moyles looks set to get an offer of a different challenge at Radio 1. Despite his reputation for laddishness, half his audience is female, and despite pushing 40 he is popular with young listeners. Vaughan too should be able to reach across age barriers.
Radio 1 is required by the BBC's licence to reach an audience of 15-29 year olds. Its median age listener is 30. Many commercial popular stations aim at an overlapping 18-35 demographic, to meet the needs of advertisers. But just as younger listeners no longer have the spare cash to spend on advertised products, so older people are more likely to listen to contemporary pop than generations past.
The 15-29 age rule is becoming increasingly unrealistic. A young generation raised on vast iPod libraries have a breadth of music knowledge that surpasses that of their parents – there's no reason why they wouldn't appreciate the specialist shows on Radio 2 or Absolute.
Meanwhile Steve Barnett, professor of journalism at the University of Westminster, said he accompanied his children to Radio 1's Hackney Weekend festival last month because he wanted to hear the young artists. Older people will listen to Radio 1 because of the music, not the age of the DJ. "It's much more cross-generational than it used to be. To penalise Radio 1 for that is daft."