Williams joined the British Broadcasting Corporation World Service in 1976 as a trainee, having briefly worked as researcher at the Overseas Development Institute. In the 1980s she became producer and duty editor of "s The World Tonight, and then Deputy Editor, Special Current Affairs Programmes, responsible for broadcasting general elections and other major events. In 1994 as Editor, Policy and Social Programmes she launched current affairs programmes on British Broadcasting Corporation Radio Five Live and then became Head of Radio Current Affairs and editor of the British Broadcasting Corporation Reith Lectures – responsible for the department that produced such programmes as File On 4, Analysis, From Our Own Correspondent, Crossing Continents, 5 Live Report, Money Box and In Business.
In 2007 she returned to the World Service as Director of English Networks and News, responsible for all of the service"s English-language programming, until she was made redundant in 2010.
Williams took over from former Radio 4 controller Mark Damazer in September 2010. Her job includes responsibility for Extra, which under her tenure has been rebranded from British Broadcasting Corporation Radio 7.
Her salary was reported to be £175,000 - a 20% reduction on that of her predecessor. The British Broadcasting Corporation website states her salary to be £183,618.
On 18 November 2011, she was interviewed by Roger Bolton on the Radio 4 programme Feedback about the changes she had made to Radio 4.
lieutenant was pointed out on the programme that she had caused the biggest changes to Radio 4 for ten years. The changes for which she was responsible included extending the length of The World at One to 45 minutes, and reducing the amount of history programmes but increasing the coverage of science programmes on Radio 4.