It is 5.30am on an ice-cold February morning and Western House is wrapped in darkness. The entrance is protected by a security buzzer. Next to a small reception desk – where uniformed guards clutch caffeine and walkie-talkies – head-high barriers prevent uninvited visitors from vaulting into the sanctum beyond.
But at this time of day there are no crowds of celebrity spotters, no paparazzi on ladders or screaming teenage pop fans. Indeed, there is nothing to suggest this is the home of perhaps Britain's greatest music and entertainment institution, save only a soothing female voice on the speakers in reception asking for "moggy- and doggie-related" texts and emails.
The most popular radio station in Europe is about to welcome a new dawn. Vanessa Feltz is already on air and the early risers among the BBC Radio 2 audience, which will swell to 15.1 million listeners during the course of the week, are tuning in to her patter. "If you haven't yet stuck a toe, a finger, even one nostril out from under the duvet, come and do it now! One, two, gulp… ooh-oh, I know, it's cold isn't it? But Radio 2 will keep you warm…"
Warmth is the key to Radio 2's success. Feltz is the entrée for a schedule that monopolises the cream of British radio broadcasting. She hands to Chris Evans, the undisputed king of breakfast, who gives way to Ken Bruce, Jeremy Vine, Steve Wright and Simon Mayo. The station's presenters range from modern-music taste-makers such as Jo Whiley and Jamie Cullum, to arts broadcasters such as Claudia Winkleman, to venerable voices of the airwaves such as David Jacobs and Brian Matthew, octogenarians both.
Western House is an unassuming seven-storey side-street block that could contain a government quango. It's a short walk from New Broadcasting House in London's West End, but lacks the glamour of BBC HQ, which was recently refurbished for £1bn and is home to Radio 1.
Yet Radio 2 has never been this popular. In a time of myriad media choice, when traditional communications brands are seeing audiences splinter under the pressure of the internet, the successor to the old Light Programme has just achieved all-time record ratings.
This, let's remember, was not so long ago a deeply unfashionable broadcaster. For a period in the late 1980s and 1990s it marked itself out as a home for the frumpy and grumpy; those who wanted to divorce themselves from a youth culture shaped by the dance-music revolution and redefined by the attitude of bands such as Oasis and Blur. With even Tony Blair embracing Britpop, thirtysomethings who should have been stepping up to Radio 2 were dragging their feet rather than participate in what the BBC would like to be regarded as an essential life stage of Britishness.
They had no desire to get old with the likes of Jimmy Young, a masterful broadcaster of his era but one known for being the "housewives' choice". Someone who cherished catchphrases such as, "What's the recipe today, Jim?" and "Orft we jolly well go," and whose phone-in callers had a reputation for the kind of reactionary views that made the show a key constituency for Margaret Thatcher during the 1980s. No, they would cling on to their youth a little longer and listen to a resurgent commercial radio sector or to Radio 1, which had renewed credibility from a schedule revamped with specialist music presenters.
So how did Radio 2 become not just relevant again, but utterly dominant in the medium? The latest ratings revealed not just a historic high for the station itself, but record audiences for Bruce, Vine, Wright, Mayo and Cullum. Weekend shows from Dermot O'Leary, Elaine Paige, Johnnie Walker and Paul O'Grady all achieved new peaks. They are, it must be said, an eclectic band.
Spending a day inside Radio 2 promises the possibility of deciphering the network's strange appeal. Feltz arrives immaculately made-up at 5am for a show that is a mixture of linguistics ("emption" is her word for the day – she read English at Trinity College, Cambridge, where she listened to Radio 2) and schmaltzy surrealism (doggie theme tunes and a Lovely Listeners Lovely Lunch Club). She talks reverentially of the network's "gentle alchemy".
At 6.31am there is something of an explosion in the lab – the station's chief scientist, Chris Evans, has announced his arrival in the building. It is doubtful that, when they wrote "London Calling" in 1979, Joe Strummer and Mick Jones imagined it as an opening number for the successor to the Terry Wogan show. But it has an immediate effect, pulsing energy through the sixth floor, from where the shows are broadcast. "The Clash on Radio 2 – welcome to another great day in your life," Evans greets his listeners.
Viewing the former Channel 4 presenter through a glass panel, which separates him from his producer's desk in Studio 6C, is akin to watching a television show. He is wearing a bright scarf, a blue hoodie and red beanie hat carrying the insignia of his favourite motoring brand, Ferrari. Into the microphone he toots an old car horn. Radio 2 has changed gear.
Evans is a broadcaster who believes in the value of preparation. Since the previous day his production colleagues have been working on features and scripting witty lines that will sound spontaneous to the morning listener. Though he is the station's most discernible star, Evans is a generous team player who introduces to the audience "The Gang Behind the Glass"; his producer Andy "Mr Tickle" Warrell, assistant producers "Tip Top Tom" Billington and "Lady Lisa" Smith, and studio manager "King Nick" King. It helps creates the sense of an event.
Evans calls on his team for "zingers" from among the 2,000 texts and emails sent in by listeners each morning. He plays music from rock bands such as the Stereophonics and rattles through the news headlines. His commentary is peppered with sound effects from a Cart Wall computer application that includes a "Hallelujah" chorus and the themes to Thunderbirds and The Magnificent Seven. After 14 minutes of this it's hard to believe it's only 6.45am. But this is how 9.52 million people choose to start their day.
The currency of "national treasure" has been devalued – but few would argue that Terry Wogan did not deserve such status within British broadcasting. When he gave up the Radio 2 breakfast show in 2009, saying goodbye to an audience of 8 million, he seemed an impossible act to follow. Yet Evans has managed to impose his own style while showing due deference to his predecessor. During a topical skit on the Papal succession, for instance, he observes: "If Radio 2 was run by the Catholic church, Terry would still be here… maybe not a bad thing."
For all the slapstick, the show is more firmly bonded to the current affairs agenda than Wogan's and the k presence of newsreader Moira Stuart adds gravitas to the zoo atmosphere of the show. Not to mention cool. The former Ten O'Clock News presenter enters the studio in long skirt and ankle boots, her spectacles perched on the end of her nose, nodding her head to "She Drives Me Crazy" by Fine Young Cannibals.
After coming off air, Evans expresses his gratitude for the platform Radio 2 offers him. "I am surrounded by the best in the business, 24/7," he says. "I still feel like the new kid. Like I'm still on work experience – which I suppose I am. I learn something new every day and relearn something every five minutes."
His career has not been without its upsets; his time broadcasting in the same slot for Radio 1 in the 1990s was blemished by repeated censure from Ofcom for inappropriate content, and a personal lifestyle of wild drinking that obsessed the tabloids. So he avoids sounding arrogant and acknowledges the dangers inherent in live broadcasting. "You're only as good as your last link, let alone your last show. When you're part of the might of the whole of the BBC, it's important you bear in mind that with such enormity comes great fragility. One loose brick and the whole shooting match comes crashing down."
Once a mogul, who sold his Ginger Media Group empire for £225m in 2000, Evans now sounds very much the BBC man. He repeatedly references BBC television and radio shows on air, especially his Radio 2 colleagues. At 46 and with two young children, he is at the heart of the station's demographic and, while he rarely allows the speed of his show to relent, he is anxious not to leave any listeners behind. "Our show sets out to be relevant, inclusive and accessible," he says. "It's a big old useful ship if sailed to even half its full potential. When I'm no longer doing it, my one regret would be if I don't make the most of the opportunities it presents." It's telling that he has introduced his own competition idea: a 500-word story-writing contest that gives children the chance to win a pile of books as tall as the presenter himself.
With nearly 10 million listeners, Evans could probably book any studio guest he liked. But that would be too easy. Instead, this morning he conducts a telephone interview with Garon Michael, the Californian monkey impersonator who appeared in Planet of the Apes and then drummed along to Phil Collins in a Cadbury commercial. "When did you become the go-to gorilla guy?" asks an excited Evans, who began his own career as a Tarzanagram.
And then, at 9.30am, the Radio 2 machine changes pace once more with the introduction of the avuncular Ken Bruce, a fixture on the network for the past 29 years. If Evans is a classic Ferrari sports car, careering around a high-banked race circuit, Bruce's motoring equivalent is a sleek limousine, which he drives on automatic.
Preparation is anathema to him. "I come on and get started and just allow a stream of consciousness." No notes at all? "Oh, absolutely not. That's the fun of it – you just go off and I have no idea where it ends any day."
Radio 2 presenters vary in the way they imagine their audience. Bruce is thinking of a single individual, though no one in particular. "You are having a conversation on the telephone – it's not standing on a stage addressing 500 people. There's hardly ever any radio listening done with more than one person in the room."
His effortless presentation is fed by banterish correspondence from listeners. "When I started here it was all postcards and it was about a week before you got a response to what you had said. You had to keep your conversational threads running a long time," he observes in a dry delivery that makes so much of what he says sound funny.
Bruce's producer, Gary Bones, is a music aficionado, and one of the show's highlights is the daily PopMaster quiz. Businessmen reputedly wait in the car park before meetings rather than miss it. Designed to be challenging, it is, says Bruce, "not a GMTV type of quiz". Bones looks for interesting contestants. Today's has the claim that his mother went out with Dave Prowse, an actor who played Darth Vader and the Green Cross Code Man. The contestant, possibly carried away by the moment, also credits Prowse for "the Jolly Green Giant" and Bruce lets him down with a gentle "Oh, I don't think so." He wins a digital radio – very much a Radio 2 prize.
The station's secret, says Bruce, is honesty. "The great thing about the people at Radio 2 is that they're not concerned about coolness or looking good," he says. "I can come in on the train every morning and be sitting asleep, drooling, and nobody knows it's me. It's the best of both worlds – I have enough attention to feed the ego but not so much as to interfere with having a good time."
Bruce's one studio partner is the traffic correspondent Lynn Bowles, who describes herself as "his office wife" – though she also appears on the breakfast show passing on news of snarl-ups from her faithful informants on the motorways (Papa Kilo, Becky's Dad etc).
At midday, Radio 2 turns to current affairs, taking four big themes of the day. For 10 years Jeremy Vine has been hosting a news-based programme which gets a similar-sized audience – though a very different one – to the Radio 4 Today programme. "People say to me, 'You used to do Newsnight and now you do Radio 2, one is very serious, the other is light,' and I think, 'You've got it completely wrong because this show is the one that can make you cry.'"
The show is driven by its callers and Vine has a connection to the public few other BBC journalists enjoy. "There is a distressed listener who is working very hard to make ends meet, a salesperson on the road or at home with the kids, and they are really feeling this economic crunch and we come back again and again to the triple dip." He refers to London as being "like a city state", with a property market that leaves many of his audience bemused. Attitudes have softened since Jimmy Young had this slot, with a "hugely increased level of tolerance" over issues such as gay marriage. But support for military families is a core value of this audience. "Today we are doing the Catholic church and [the entry into the EU] of Romania and Bulgaria – and we manage not to lose audience. That is the most exciting thing for me, to do news in a non-news setting."
The entertainment resumes at 2.03pm with "Steve Wright in the Afternoon". Like Evans, Wright is a veteran of Radio 1. When asked to make the switch by Jim Moir, the controller who kick-started Radio 2's change in fortunes with a shake-up in the schedule at the end of the 1990s, Wright responded, "Agh, no!" Moir told him he was ditching the Frank Chacksfield orchestra and playing Coldplay and the Kinks instead. Wright has been in his current position on the network for 14 years and, of all the presenters I meet, he is the friendliest and most accommodating.
"We will be talking about steam-cleaners," he says, in a statement of apparently limited ambition, just before k going on air. But Wright commands an audience of 7.86 million – which explains why David Cameron came on the show looking for votes. Like Evans, Wright is very much a forward-planner. He comes in at 9.30am to "prep hard". Celebrity guests are booked and slots are created for regular contributors such as the misfit "Barry from Watford" and "Old Woman", who reminisces about the Blitz.
He thinks of the heart of his audience as the baby-boomer generation, and his tone is unapologetically upbeat. He is allowed a "few nice toons" alongside the playlist selection and he always chooses "summer-y" tracks. "There's a little bit of electric piano in there, a little bit of saxophone. We do try to be cheery."
Steam-cleaners are important because of their "relatability" – everyone spills coffee on the carpet. He is struggling to control his weight and one of his interviewees today is the diet author Janet Thomson. Before the show begins he treats me to his Alan Bennett "liners", recorded by the impressionist Jon Culshaw. "I rather like it when Tim talks about golf, I can picture him thurr, in his trousers. And joompah." It's the sort of surreal material that Wright has made his career on. "It doesn't necessarily have to make sense at all; sometimes it's just a mood, just an atmosphere," he says, in what is as good a description of the appeal of Radio 2 as I've heard.
Finishing lunch in the BBC club on the ground floor is the station's great stalwart David Jacobs, who will be 87 in May. Listening to his own show in bed on Sunday evenings is the highlight of his week, "because there isn't a song, a melody that [producer Alan Boyd] and I haven't chosen because we absolutely love it and can't wait to play it". He records "five or six programmes in a day", writing the numbers 1 to 15 on a piece of paper and choosing his running order from a Western House filing cabinet filled with CDs and marked: "The David Jacobs Collection". Unlike Bruce, he broadcasts his easy-listening selection to an imaginary "family which includes all generations". The programme should be "a bit like a symphony", varying tempos and vocal styles.
He is the former host of the BBC1 pop show Juke Box Jury and chairman of the Radio 4 quiz Any Questions? But nowhere has looked after him like Radio 2: "I'm at home at Radio 2. I was never once asked to a Radio 4 party. They saw me as light entertainment. The doorman at Radio 4, had there been one, would not have held it open for me."
On the fourth floor sit the Radio 2 controller Bob Shennan and his head of music Jeff Smith, who has the critical role of deciding on a weekly playlist of "timeless, melodic music" which "gives a spine to the station". Consisting of 80 per cent oldies and 20 per cent new material, it is drawn up by the station's producers at a meeting held on Wednesdays at noon.
Shennan, who also oversees the digital network BBC 6 Music, says he finds it easy to persuade presenters to work for such a golden channel as Radio 2. He'd like the network to become more visual, making greater use of the potential of social media and red button technology. But he acknowledges "evolution" in Radio 2's fortunes, beginning with Moir's changes of 15 years ago and continued by Shennan's predecessor Lesley Douglas, who was brought down by the Jonathan Ross/Russell Brand obscene voicemail scandal in 2008. That episode was "a real shock to the system" but the lesson has been learnt. Ken Bruce had earlier conceded that the incident had provoked a compliance clampdown and "the rest of the BBC were a bit annoyed with us for a while".
Back on the top floor, Simon Mayo is at the microphone. He regards the playlist as the network's signature. "I firmly believe that the argument for Radio 2 should start and finish with the playlist. We play a wider range of music than stations that would be considered our competitors," he says. A more serious figure than his colleagues – on this day at least – he is another former breakfast show host on Radio 1 and in a good position to compare the "Nation's Favourite" of the 1970s and 1980s with Britain's current most popular station. On Radio 2, he says, the presenters are settled and not looking to undermine each other. "I have found it to be not bitchy at all and no one seems to have a bad word for anyone else. It doesn't have that clashing dinosaur feel; when I joined Radio 1, that's what it felt like. There were these huge monster programmes that delivered incredible audiences, but you were working with pop stars and that could be slightly hairy at times."
As Radio 1 now tries to cope with a cultural shift, in that the young audience it is required to serve no longer buys radios, Radio 2 continues to grow. "We have students and pensioners – I love the feeling that we want everyone to listen," says Mayo. "Once Radio 1 has left you behind – or you have left Radio 1 behind – we are there to welcome everybody to our lovely Jacuzzi of a radio station. It's a bit like finally admitting you are a 34 waist rather than a 33 – there's a great freedom and liberation."
That transition is aided by the presence in the schedule of Jo Whiley, who is pre-recording her evening show while juggling plans for a school parents' evening. A young- looking 47-year-old with four children, she also reflects the demographic of a station whose average age of listeners is 51. Her studio Cart Wall contains a mixture of cool "jingles" and "idents" from artists such as Maverick Sabre, Kyla La Grange and Ed Sheeran. "As you grow older you don't stop loving music," she says. "It's one of Radio 2's strengths that it acknowledges that."
Radio 2's evening and weekend schedule contains an enormous breadth of specialist music programmes from the likes of former Old Grey Whistle Test presenter Bob Harris to the blues singer Paul Jones. Tonight the jazz musician Jamie Cullum is doing a duet on his own show with the singer Alice Russell. They rehearse in the Radio 2 green room area using a piano donated by Sir Elton John (the one he used to compose music for The Lion King, apparently). Steve Wright is still around, a couple of hours after coming off air. He is in his element in this building, watching Cullum rehearse, chatting with colleagues and joking about his fondness for buying steam cleaners and gadgetry.
Despite his stage experience, Cullum says he did "50 or 60 dry runs" in the Radio 2 studios before he felt comfortable enough to broadcast live. "The logistics of pressing the right buttons, getting the timings right and not swearing on the air – those things are quite scary. But after 20 or 30 live shows it feels natural and never less than exciting," he says. Performing two tracks, Cullum and Russell manage to create the mood of an intimate club in an upstairs corner of the now nearly deserted Western House.
Just after 8pm, Whiley's show begins, highlighting breakthrough acts such as Woodkid and the Staves. She is encouraging listeners to send in their mixtapes. The moggies and the doggies of early this morning seem a very long time ago.