1999–2002 A transfer to radio came on 19 September 1999 when she joined
BBC Radio 1. She launched
The Surgery with
Mark Hamilton, where Cox acted as "Nurse Coxy". She also co-hosted the Saturday lunchtime show with
Emma B from 13:00 – 15:00 In December 1999, it was announced that Cox would replace
Zoe Ball as presenter of
Radio 1 Breakfast. Cox's breakfast show stint began on 3 April 2000. Initially, her listening figures grew from 6.9 million to 7.8 million listeners during her first fifteen months in the job — earning Radio 1 its largest breakfast audience ever — higher than that of her predecessor and ex-
BBC Radio 1 DJ
Chris Evans. By August 2002, however, numbers had dipped back under 7 million.
2003–2008 In January 2003, Cox denied rumours that she was preparing to leave the BBC for a rival show and signed a three-year contract with the public service broadcaster. In August 2003, the BBC again denied rumours, reported in the
Daily Mail, that she had been given ten weeks to increase ratings, or to face replacement. However, two months later, the BBC announced that Cox, whose listening figures had slipped to 6.6 million, would be replaced by
Chris Moyles in January 2004. Cox hosted her final breakfast show on 19 December 2003. Cox then presented the afternoon "drivetime" slot, effectively swapping shows with Moyles. She hosted the Drivetime show for six months with features such as "For Your Ears Only", "Me, Myself and I", and "Chap's Eye Pub Quiz" (referring to her former sidekick
Mark Chapman). At the end of May 2004, Cox began her
maternity leave to give birth. Before she returned to Radio 1 in early 2005,
Scott Mills, the presenter who took over her slot during her maternity leave, was given the drivetime slot permanently. From February 2005, Cox took over the afternoon show (13:00 – 16:00) on Saturdays and Sundays.
2008–2014 On 17 February 2008, Cox presented her last show for six months before leaving for maternity leave to have her second child.
Annie Mac presented the show during her absence until Cox's return in September 2008. Cox and Annie Mac both later covered for
Jo Whiley who was on maternity leave between 29 September 2008 to 20 February 2009. Following Whiley's return, Cox returned to weekends to present a Sunday mid-morning show, broadcasting between 10:00 and 13:00. In March 2010, Cox went on maternity leave for the third time, with new presenter
Matt Edmondson providing cover. She returned to the station on 9 August 2010 to cover for
Fearne Cotton for three weeks. Cox made a self-confessed "unexpected" return to the breakfast show on 2 and 3 September 2010, as she sat in for the ill Chris Moyles. In August 2012, it was announced that Cox,
Gemma Cairney,
Huw Stephens,
Jameela Jamil,
Alice Levine, and Annie Mac would cover Fearne Cotton's show on BBC Radio 1 weekdays from 10:00 to 12:45, whilst Cotton was on maternity leave, until Cotton's return in September 2013. After Cotton's return, Cox presented various cover shows; her final show for Radio 1 was on 17 February 2014. ==BBC Radio 2==