Watt began his career as a political reporter based in Belfast working for The Times as Ireland Correspondent, covering the initial stages of the peace process.[2][3]
In 1997, he was based in London following his appointment as political correspondent for The Times,[3] before joining The Guardian a year later where he worked as European editor and chief political correspondent.[2][3] Between 2007 and 2008, he was the acting political editor of The Observer.[3]
In 2012, he appeared on Press Gazette's list of the 'top 50 political reporters', at number 14.[4]
In 2016, Watt left The Guardian to become political editor of Newsnight on BBC Two, replacing Allegra Stratton.[2] The editor of Newsnight at the time was also a former Guardian employee, Ian Katz, who said that Watt was "one of the most trusted, authoritative and engaging journalists in the country. With a background in Northern Ireland, Europe and Westminster he's also uniquely equipped to guide viewers through an increasingly fractured and complex political landscape." A number of BBC journalists were reported to be "annoyed" with the director of BBC News, James Harding, appointing figures with backgrounds in the newspaper industry, including Watt, to BBC posts.[5]
In March 2019, he recounted a comment with strong language made by an anonymous cabinet minister under Theresa May.[6]