Andy Parfitt leaps to his feet and rushes to the window as a crescendo of shrieking voices threatens to shatter the glass. But the fans are not there in his honour, even if he is finally bowing out of BBC Radio 1 after 13 years, the longest-serving controller in the history of a network devoted to entertaining British youth.
"Oh, here they are," he says, looking down from the first floor at the Radio 1 entrance and acknowledging that the screaming fans are camped out for the boy band JLS, not for a 52-year-old broadcasting executive, even one with a thick head of blond hair who comes to work in trainers and who curls his legs up beneath him on the chair, just like a teenager.
After 32 years at the Corporation, Parfitt is still a BBC "suit" – albeit its former "Teen Tsar". If anyone was tearful and emotional when Parfitt departed the station on Friday, it was more likely to have been a grown man like himself. Someone like Chris Moyles, the 37-year-old breakfast presenter who has been loyally protected by his controller as he has amassed an audience of eight million. Or Tim Westwood, another fiftysomething, who – with Parfitt's backing – has ensured that Radio 1 remains the first port of call in Britain for hip-hop's royalty.
Even Parfitt's biggest rivals in the commercial sector of the radio industry would find it hard to dispute that he is going out on a high. A couple of years after he took the post, he was shown graphs which projected that the station's audience of 9.44 million was facing further inevitable and long-term decline. Internally, the BBC was wrestling with the notion of what Radio 1's role might be when it had only four million listeners. But as Parfitt leaves, the revitalised network has a record audience of 11.8 million, even as young people are turning their backs on traditional media platforms.
If there are criticisms of Radio 1, they tend to be that it is too mainstream and that it attracts an audience beyond the 15-to-29 age group which is its remit. Parfitt concedes that the median age of the audience is 30 and that the figure is "a very difficult measure to move", partly because – rather like Moyles, Westwood and another Radio 1 stalwart, Annie Nightingale – the listeners are reluctant to move on. "An interest in popular culture and young things is a prevailing interest of everybody," Parfitt says. "It's not hard to understand why people don't reach their 30th birthday and hit the off button on Radio 1."
The key to Parfitt's longevity has been his ability to refresh his schedule with new talent, to manage the egos of his stars and, above all, to analyse the data and identify what young people really want to listen to. He arrived at Radio 1 as an assistant to Matthew Bannister, the controller who culled the "Smashie and Nicey" presenters who had built the station into the "nation's favourite" but overstayed their welcome. As controller from 1998, Parfitt made his own changes, at first with limited success. He has at times been radical, putting Moyles into the breakfast slot in 2004 in place of Sara Cox, and giving a platform to specialists such as Pete Tong, who credits him with establishing dance music on Radio 1. But he also rowed backwards when listener research demonstrated the risk of being in hock to the cool "scenesters" and frightening away the teenage masses that he was obliged to connect with.
The insight he enjoys as head of the BBC's youth station saw him add the title of "Teen Tsar" in 2006 to a business card that already recorded his controllership of Radio 1, the digital stations 1Xtra and Asian Network, plus his responsibility for the BBC's Popular Music across all media. The digital revolution might have been a frightening experience for a then fortysomething executive, but Parfitt benefited from being at a publicly funded organisation with a licence to experiment. "When the web came along it was an opportunity to show pictures of the DJs and artists and to get information out there.
"The Radio 1 audience has never on the whole read the Radio Times. Technology has felt like an opportunity rather than an ominous doom-and-gloom threat."
When Facebook became popular "our teams were all over that straight away", he says. Parfitt is techy by nature. He joined the BBC as a trainee studio manager after an uninspiring spell at the Bristol Old Vic Theatre School, where he learned sound and stage production. "My ambition in my late teens was that I wanted more than anything I could ever imagine to be John Peel's sound engineer," he confesses. He achieved that ambition before becoming the controller of the station where Peel worked until his untimely death in 2004.
More recently he has championed young presenters including Gemma Carney and Matt Edmondson, and a concerted strategy in the past 18 months has seen an increase in listeners under 15. Nonetheless, he recognises an underlying problem with the decline in listening hours among young people. "The danger is of a two-tier radio culture in this country," he says. "You could imagine a world where there is a younger cohort of people for whom radio is a small part of their world and an older audience that are listening for longer and longer to their favourite stations."
Parfitt is not leaving the BBC altogether. He will take some of his insights into a new part-time role working for Tim Davie, the BBC's director of audio & music. He will also work for Comic Relief and hopes to pick up other offers from the commercial sector. "I'm going to expand my horizons and broaden my experience."
He has encouraged staff at Radio 1's Yalding House headquarters to develop a more informal culture, without the security turnstiles of other BBC buildings. That might be lost when the station moves to the top floor of the refurbished Broadcasting House (five minutes' walk away) next year. It's the end of an era – although Parfitt himself insists that the network retains its original ethos. "I have always been very clear with all the DJs and in my own mind that Radio 1 was invented in September 1967 and presenters come and eventually go, whoever they are, as do controllers."
For all the screaming fans and the famous rock stars who pass through the building, he doesn't seem to be in the job for dropping names and spinning yarns – one of his strongest memories is the nightmare of visiting Tim Westwood in hospital after he was shot in 1999.
While Parfitt can no longer play Peter Pan at Britain's youth station, he's not about to become a grumpy old man. "Young people are blamed for everything these days from easy exams to smoking, obesity and taking drugs," he says. "At Radio 1 we celebrate the great things about being young – the music, the events, the energy and optimism."
* Parfitt started his professional life as a stage manager in his native Bristol after leaving the Old Vic Theatre School, where he learned sound and stage production. He said as a teenager he wanted "more than anything I could ever imagine" to be John Peel's sound engineer.
* He joined the BBC as a studio manager in 1979 and took up a British Forces Broadcasting Services secondment to the Falklands. He worked as a producer with BBC Education and Radio 4 before joining Radio 1 as chief assistant to controller Matthew Bannister in 1993. He was appointed controller five years later.
* Parfitt oversaw changes in Radio 1 including the launch of 1Xtra in 2002.
* He climbed Mount Kilimanjaro for Comic Relief in 2009, along with Radio 1 presenters Chris Moyles, Fearne Cotton and other celebrities.