There's always a gaggle of ageing autograph hunters lingering around the door of Western House, the central London home of BBC Radio 2 along with its newly famous sister station, BBC 6 Music. This is a spot where the stars come thick and fast. As I arrive, the big-haired soul diva Macy Gray heads into the lifts with her entourage. On the fourth floor, the London singer Jamie Lidell is performing live for an enthusiastic Lauren Laverne, star presenter of 6 Music.
That morning another powerful figure had stepped through the portal of Western House, ignored by the paparazzi in spite of being dressed all in black, like Johnny Cash. The boss of Britain's most popular radio network says the autograph collectors never trouble him for his signature, and admits that the individuals who do arouse a frenzy of flash photography and proffered ballpoints are often figures of mystery to him. "I hardly ever know who they are," he admits. "I have to ask: 'Who's in today then?'"
Yet Bob Shennan is a friend to the stars. As controller of both Radio 2 and 6 Music, he employs Chris Evans and Graham Norton, Jarvis Cocker and Cerys Matthews, Dermot O'Leary, Jeremy Vine and Alan Carr. Radio 2, which he says should be "the home of the Britain's finest entertainers", is enjoying unprecedented success, with a weekly audience of 14.6 million (almost one quarter of the population). And 6 Music, as a result of the clamour that surrounded its proposed closure, has never enjoyed such a profile in its eight-year history.
Shennan, 48, inherited Radio 2 at a time of great turbulence, in the wake of the resignation of his friend and predecessor Lesley Douglas, who resigned over the infamous Sachsgate affair. As well as trying to restore the network's damaged reputation, he has spent his first 18 months trying to manage what he describes as "the biggest single change in UK radio that I can ever recall", namely the departure of Terry Wogan, a breakfast-time institution for generations of BBC listeners.
Shennan says that though he anticipated "quite a lot of churn in the audience", he has faith in Chris Evans. "Although losing such a brilliant and instinctive broadcaster as Terry Wogan is a big loss, Chris Evans is so overwhelmingly his heir apparent that I felt very confident that he will prove his worth to the audience over many years in the same way that Terry has."
Shennan denies that the switch was intended to win a younger audience for Radio 2, saying that the average age of its audience is stable, at 51. "We don't want to alienate the huge audience that we already have. The success of Radio 2 over the last decade has been that it has been based not on old-fashioned demographic targets. Our presenters have broad, multigenerational appeal."
No sooner had he replaced Wogan (who continues to broadcast for Radio 2 on Sundays), than Shennan lost another key figure. After more than a decade with the network, Jonathan Ross parted company with Radio 2 last Saturday, leaving the controller to mourn a presenter who he says was "unquestionably the pivotal force in the renaissance of Radio 2" in the past decade: "I hope that he's left the BBC in such a way that he's left the door open at one point in the future to come and do some more things." Shennan has lined up Norton as Ross's Saturday morning replacement.
Lancashire-born Shennan rejoined the BBC from Channel 4 in 2009, where he had been stranded after the cash-strapped commercial broadcaster aborted its ambitious plans to go into digital radio. "It was great that I went to Channel 4, because if I hadn't I wouldn't be here, and this is the best job in radio," he says philosophically. When the repercussions of Sachsgate were raging, Douglas – who is now a senior executive at Universal records – encouraged Shennan to go for her old job.
He saw the recent BBC Trust's review of his stations as another learning experience – even though it led to the Corporation's executive recommending that 6 Music be closed down.
The review "enabled me to know more about Radio 2 and 6 Music than anybody else, because I had to be completely researched and on my toes," he says. Though the threat to 6 Music provoked outpourings of anguish from some of the presenters, and from angry listeners – who deluged the BBC Trust with 25,000 emails – Shennan talks of the process with such enthusiasm that the widely aired notion that the BBC was never serious about closing the network is hardly dispelled. "When the decision was taken that this was the executive recommendation, I think I thought it would be closed down," he says eventually and with little emotion.
It might be that he is anxious not to be disloyal to his boss Tim Davie, the BBC director of audio and music and the driving force behind proposals to slim down the number of BBC radio brands. Did he argue that a great mistake was being made? "It's fair to say we were properly exploring all the different aspects of the music radio portfolio," he says. "One of the really important things we discussed was the fact that whatever you called things, there's a really valuable purpose that the BBC serves for the development of new music and artists in the UK." 6 Music, he notes, plays more different songs in a week than any other station.
So wasn't it absurd to propose closing it down? No, says Shennan. "Isn't that what you'd expect a public service broadcaster to do, to ask itself this kind of question and then be up-front enough to change its mind corporately?"
The process also encouraged a campaign of support for the BBC's output at a time when it is under pressure to scale back its ambitions. Shennan's priority now is to improve the way Radio 2 and 6 Music (with its average age of listener at 37) work in tandem. "They share the same DNA," he claims. Radio 2's doubtful reputation for musical innovation will be helped by its "taking ownership" of the BBC Electric Proms, the festival of collaborative concerts in October, formerly shared among BBC networks.
Shennan, who headed BBC Sport before overseeing Radio 5 Live for some eight years, goes to more gigs and musical theatre than he used to. To show support for 6 Music, he has experienced Glastonbury for the past two years.
He points out that when England lost to Germany, he was at the festival's Pyramid Stage watching the guitarist Slash. But his up- coming holiday in Spain is less rock'n'roll. "I'm going to play golf," he says.