Within six months, Van Outen - Vaughan's third co-host since he replaced Chris Tarrant as the Capital Breakfast Show's presenter - had left, and the station was lagging behind Magic and Heart in the London ratings.
But Capital now seems to have found a winning combination in Vaughan and Lisa Snowdon - the model, TV presenter, Strictly Come Dancing sensation and ex-girlfriend of George Clooney.
For the fifth consecutive quarter, the station held on to its position as the most popular commercial radio breakfast show in London, outstripping nearest rival Heart by 200,000 listeners in the latest Rajars.
'We think we have found a combination that has stuck,' says Paul Jackson, group programme director at Global Radio, Capital's parent company. 'Johnny is a vibrant, energetic character and he and Lisa absolutely click. You cannot fabricate that kind of chemistry.'
Bright Young Things director Niall Cowley says Snowdon has the clout to match Vaughan. 'Her Strictly Come Dancing and Britain's Next Top Model jobs dovetailed beautifully, making her one of the most sought-after celebrities in London,' he says. 'When we get wish lists from clients, she is always top.'
Helen Moore, editorial services director at markettiers4DC, says: 'Capital is increasingly doing a great job of owning London. We have incorporated it into a number of campaign strategies for clients trying to reach the cool, London-centric "it girl" audience.'
Since Global bought Capital's former owner, rival radio company GCap, the station has blossomed. Jackson says: 'We have really focused on getting it back to being a core hit music station. The breakfast show is in good shape, and pop artists know they have to be on Capital if they want to be successful.'
Moore agrees: 'While traditional opportunities are limited because Capital is used to interviewing A-listers and people with high media profiles, a strong opportunity does exist for relevant events happening in the vicinity, especially if there is celebrity attachment.'
Capital's own events programme reflects its clout in London. Its annual Jingle Bell Ball has been extended to two nights this year and will feature performances from pop heavyweights including Janet Jackson, Lady Gaga, Alexandra Burke and Shakira.
James Herring, joint MD of Taylor Herring, says: 'Getting out there and mingling with London off-air is really important and it seems to be working for Capital.'
Audience: 1.62 million listeners (Source: Rajar)
Frequency: 95.8 FM
A MINUTE WITH ... Paul Jackson, group programme director, Global Radio
- What is the competition like for Capital?
There are a lot of good breakfast shows in London, but for us the main competition would be The Chris Moyles Show on BBC Radio 1.
- How did you react to Moyles goading Johnny Vaughan when he joined Capital?
- We didn't, and don't, take that kind of thing seriously. We just got on with it.
- What makes an ideal feature or guest?
We cover big London events. We do red-carpet premieres at Leicester Square and have the stars on. We work with all the big London organisations. But our audience tends to want the likes of JLS and Lady Gaga. We have LBC for more serious topics and guests.
- Tell us about your charity, Help a London Child
We are doing a big push at the moment. Lisa Snowdon is jumping out of a plane and drive-time presenter Greg Burns appeared in Priscilla, Queen of the Desert and ran a half-marathon. We try to keep the momentum going year-round, but a couple of times a year we really focus on it.