King served as political advisor to Nobel Peace Laureate and First Minister of Northern Ireland David Trimble for six years (1998–2004).
He was the Ulster Unionist party negotiator on equality, human rights and cultural issues in the multi-party talks leading to the Good Friday Agreement.
At Stormont, he was responsible for political communication strategies, party management issues and drafting position papers.
He left formal politics in 2005 to work in public relations, initially assuming responsibility for dealing with the reputational issues arising from the Office of Fair Trading inquiry into alleged fee-fixing for the Independent Schools Council, before becoming External Relations Director for Policy Exchange (2006–2008), a centre-right think-tank, then, latterly, as a director of APCO Worldwide (2008–2012), the global public affairs and communications firm King's marriage, in 2005, to Jean-Claude Madrange was publicly denounced by the DUP politician Ian Paisley Jr.[1] In August 2010, an inquest at St Pancras Court in London found that King's partner, Jean-Claude Madrange, had taken his own life on 8 May.
St Pancras Court was told that Mr Madrange was struggling with bipolar disorder and had tried to commit suicide by taking an overdose one month earlier.