Royall was a special adviser to Neil Kinnock, the Leader of the Labour Party, in the 1980s, and she has remained a close ally of his ever since. She sought selection as Labour's candidate for Ogmore in a 2002 by-election. However, the constituency party preferred Huw Irranca-Davies as their candidate. When in 2003 she became head of the European Union's office in Wales, there were calls for her to stand down because of her connections to the Labour party.
On 25 June 2004 she was created Baroness Royall of Blaisdon, of Blaisdon in the County of Gloucestershire. In the House of Lords, she became government spokesman for Health, International Development and Foreign and Commonwealth Affairs.
On 24 January 2008 Baroness Royall was appointed government Chief Whip in the House of Lords, following the resignation of Lord Grocott, and was created a Privy Counsellor later in the year. On 3 October 2008, she was promoted to the cabinet by Gordon Brown, who made her Leader of the House of Lords andLord President of the Council. On 5 June 2009, Royall was succeeded as Lord President by Lord Mandelson, the Business Secretary, and was appointedChancellor of the Duchy of Lancaster.
She voted for a 100% elected House, on the last occasion that the House of Lords voted on Reform of The House of Lords in March 2007. She has called for a national Referendum on any reforms of the chamber.
She was married to Stuart Hercock until his death in 2010, and has a daughter, Charlie, and two sons, Ned and Harry.