Even a few years ago such a scandal involving Radio 2 would have been unimaginable. So how did the station shed its “pipe and slippers” image to become the venue for obscene phone calls from a former heroin-using comic?

Dial switchers used to rely on the middle-of-the-road “easy-listening” station, set up in 1967, for light organ music and cosy chat from Jimmy Young, but a change of strategy to attract younger listeners with big-name presenters has turned Radio 2 into a ratings juggernaut which, commercial rivals argue, is destroying their business.

Under Lesley Douglas, right, the Controller who took over in 2004, Radio 2 has wooed an audience of thirtysomethings, alienated by Radio 1’s “yoof” obsession but who still like their rock music and want it delivered by informed presenters.

Young was pensioned off and replaced by Jeremy Vine. Chris Evans was rehabilitated in the drivetime slot, despite protests from some listeners about his laddish past. Jonathan Ross was let off the leash on Saturday mornings, free to play his favourite mix of David Bowie and punk classics. Edgy comics, such as Mark Lamarr and Jo Brand, fill in when Ross is away. Brad Pitt joined the celebrities who voiced documentaries on their musical passions for the station.

With Terry Wogan keeping the traditional audience happy at breakfast time, Radio 2’s listenership soared to a record 13 million listeners.

Record company bosses describe Ms Douglas as “the most influential person in the British music industry” because her patronage of a new artist can make or break their careers. Most controversially, Russell Brand was brought to BBC Radio by Douglas, initially to present on the digital 6 Music station, also under her remit, before being transferred to Radio 2.

Although given a low-profile Saturday evening slot, the move ensured that Brand, then a rising star, was not available to commercial rivals.Podcasting technology, embraced by Radio 2 listeners, means that a live programme is no longer a “one-off”. Shows with Ross and Brand are listened to by hundreds of thousands more during the week than on Saturday and have an international audience via the web.

However, Ofcom has already criticised editorial failings at Ms Douglas’s stations after the Brand and Liz Kershaw shows on 6 Music were found guilty of deliberate deception during phone-ins.

She was not aware of the scams. Similarly, it is believed that she did not hear the Brand broadcast before it was aired.

Celebrity agents bring their clients to Ms Douglas first. A BBC Trust report into star pay found that the salaries being paid “to a small number of top talent working in network radio are much higher than those offered on commercial radio”.

One of Ms Douglas’s colleagues said: “Her great skill is picking presenters you would not have imagined on Radio 2 and making them work.”

However, regulators are likely to conclude that a performer who thrives on controversy, such as Brand, who records his shows through an independent production company, needs to be under closer managerial scrutiny.

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