In a shock for the long-time market leader, Capital has found itself overtaken by Heart and Magic for the first time. Magic increased its share from 5.1% last quarter to 5.3%, according to figures for the July-September quarter released by Rajar.
GCap's London flagship was hit by the defection of listeners from Johnny Vaughan's breakfast show, and its share fell from 6.1% to 5.1%.
GCap shares were this morning down 12p or 3.6% to 316p.
Whereas Vaughan brought in 1.08m listeners last quarter, only 893,000 tuned in this time. Over at Heart, Jamie Theakston increased his audience from 720,000 to 883,000, nearly claiming the commercial breakfast crown.
Ralph Bernard, GCap Media chief executive, called the company's overall results "disappointing but not unanticipated", whereas Phil Riley, Chrysalis Radio chief executive, praised the "great appeal of the new Jamie Theakston breakfast show".
Dee Ford, Emap Radio group managing director, said Magic had further strengthened its position in London. Emap's ambition of making Magic number one could be helped by the ad campaign it launched at the end of the survey period and new breakfast host Neil Fox. He starts with 645,000 listeners after the breakfast show lost 57,000 during the quarter.
Those observers worried about the volatility of Rajar figures will pick up on several large swings in share among the smaller London stations.
Chrysalis-owned LBC has now gone from 2% in the first quarter, to 3.7% in the second quarter, to 2.9% in the current quarter.
GCap's Choice FM's share halved from 2.6% last quarter to 1.3% this quarter, while its indie station Xfm increased its share from 1.6% to 2%.
Emap's Kiss FM stuttered, falling from 4.1% to 3.5%, and Guardian Media Group's Smooth FM dropped from 1.9% to 1.3%. The station was rebranded from Jazz FM in early June.
The overall picture showed commercial listening share continuing to move away from local stations to national or multiregional brands.
However, national commercial stations TalkSport and Virgin Radio saw no movement in share, holding at 1.8% and 1.5% respectively. The third national station, GCap's Classic FM, lost share from 4.3% to 4.1%.
GCap's Bernard said: "Addressing audience issues is a key focus for GCap. This was the rationale behind our recent cost restructure, which will enable us to target reinvestment in our priority areas."
The BBC's radio network had a good quarter, pushing its share up from 54% to 54.6%. Its only national station to lose share was Radio 2, down from 16% to 15.6%. Radio 1 was up from 9.2% to 9.4%, Radio 4 was up from 11.2% to 11.5%, and Radio 3 and Radio Five Live each increased share.
Breakfast listeners slipped away from Radio 4's 'Today' programme, down to 6.07m from 6.32m, and from Radio 2's Terry Wogan, down from 8.06m to 7.67m.
However, they continued to join Radio 1's Chris Moyles, up to 6.52m from 6.26m.
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