The BBC gets it in the neck whenever Nigel Farage appears on Question Time. “Ridiculous,” said SNP spokesman Michael Russell when the former Ukip leader popped up in March for his 32nd appearance on the show; and Andrew Adonis called for Ofcom to look into what he called “the BBC’s constant promotion of Farage”.

But turn from BBC television to commercial radio and we find that Nigel Farage has his own daily show on LBC radio, the station that is becoming one of Britain’s media success stories. Every weekday evening at 7pm he’s there on LBC – Leading Britain’s Conversation, as the station’s slogan has it – and he’s banging the drum for Brexit. There’s no glimmer of any of the usual impartiality of UK broadcasting, and his topics range from abortion (he was against the repeal of Ireland’s eighth amendment) to whether he’s still running a campaign for a Nobel Peace Prize for Donald Trump (it’s on hold).

This may make liberals’ teeth grind, but the Farage show is often an entertaining hour of radio and he is a natural broadcaster. He slots in well to a station that is becoming notable for two things: the punchiness of its editorial proposition, and its ability to unsettle the BBC because of its startling growth in audience. Since LBC went national, its number of weekly listeners has increased from 1.3 million in 2014 to 2.2 million in the most recent 2018 survey; and that includes a growth of 65 per cent in the number of younger listeners (aged 15-34) contributing to what one broadcasting rival calls “an amazingly well balanced listener age profile”.

Despite the Farage and Nick Ferrari factor, it would be wrong to assume that this has been achieved by becoming a British version of America’s right-wing talk radio. LBC insiders are squeamish about suggestions of a shift away from UK radio traditions, and “opinionated news broadcasting” is their preferred positioning. Also on the station and clocking up more than one million listeners is the left-leaning James O’Brien, whose shows are frequently a lament about the awfulness of Brexit; the former 5 Live stalwart Shelagh Fogarty; and Channel 4 News’s Matt Frei, who takes his Saturday morning programme in a markedly different direction to Farage’s Sunday equivalent.

The BBC is uneasy about what is happening at LBC. “Surprised” is one of the milder adjectives used by an executive when asked to assess how LBC can broadcast a regular show by an elected politician like Farage within the Ofcom impartiality framework. If you happened to tune in only at a particular time each day, you would hardly be getting a balanced picture – and LBC has exploited to its full the idea of “due impartiality”, which allows broadcasters to aim for impartiality across the totality of their output rather than within a single edition of a programme.

Among the ranks of BBC producers, there are those who find this idea more attractive than the robotic balance of “this person says yes, this person says no” that can be the corporation’s default. That’s particularly the case on 5 Live, where the figures are heading downwards. Twenty years ago, 5 Live was a reinvention of speech radio; but its audience is being nibbled away by dedicated sport and news stations – and some of its editorial rationale is lost in an age of social media. Staff there express admiration for LBC’s interaction with its audience and the strength of its personality and they muse about whether they might be able to follow suit by having, for instance, consecutive shows that represent different points of view.

It’s one possible response to the challenge I noted here last month about some BBC presenters displaying their political colours on social media – so why not on air too?

Radio 4 is not immune from the LBC factor. The network has long obsessed about its “replenisher” audiences – the younger people aged 35 to 54 who need to move over to Radio 4 to replace, frankly, those who are dying off. But LBC’s success in making speech radio attractive for younger people might add to the corporation’s difficulty in those demographic groups. At its heart is the question of whether LBC points the way to broadcasting for our noisy, disputatious times, and the extent to which the traditional model is under threat.

It is striking that many of the most memorable moments of political radio in recent years have not happened in their customary home of the Radio 4 news programmes. It was Iain Dale on LBC whose polite but deadly questioning skewered Theresa May on whether she would now vote Leave in a second EU referendum, and it was Ferrari who dominated the headlines with his Diane Abbott interview during the election campaign. Elsewhere, the BBC’s rising star Emma Barnett has achieved similar results on 5 Live and on Woman’s Hour with Theresa May and Jeremy Corbyn respectively. LBC’s additional twist on this is to give politicians their own shows, so Jacob Rees-Mogg was added to the roster to take his place alongside regulars like the London Mayor Sadiq Khan. These more relaxed formats generate newspaper headlines.

This is amplified by energetic use of social media. LBC has 14 cameras in its studios in Leicester Square, and branding that’s impossible to miss. And the best bits of the content are deployed across multiple digital platforms, with something such as Maajid Nawaz’s interview with Jordan Peterson reaching 600,000 people on YouTube.

It would be churlish not to applaud LBC’s entrepreneurship, and its casting of a boulder into the calm water of radio. It deserves to succeed. But we need to make sure this doesn’t become the thin end of the wedge for an Americanisation of our broadcast media in which opinion drives out news.

Roger Mosey is the Master of Selwyn College, Cambridge, and a former head of BBC Television News