Lloyd Jones was born on 31 January 1952, to William Elwyn Jones and Annie Blodwen Jones (née Lloyd-Jones). He was educated at Pontypridd Boys' Grammar School. He studied law at Downing College, Cambridge: he graduated with a first class Bachelor of Arts (BA) degree, later promoted to a Master of Arts (MA Cantab) degree, and a first class Bachelor of Laws (LLB) degree.
Lloyd Jones was a Fellow of Downing College, Cambridge from 1975 to 1991. From 1999 to 2005, he was a visiting professor at City University, London. He has written articles that have been published in a number of academic journals specialising in law.
Lloyd Jones was called to the bar in 1975 (Middle Temple). He became a Recorder in 1994 and served as a junior Crown Counsel (Common Law) from 1997 to 1999. Lloyd Jones became a Queen's Counsel in 1999. In 2009, it was revealed that he had been paid more than £1 million for his involvement in the Bloody Sunday Inquiry.
On 3 October 2005, he was appointed as a High Court judge, and was assigned to the Queen's Bench Division. He served as Presiding Judge on the Wales and Chester Circuit and Chairman of the Lord Chancellor's Standing Committee on the Welsh Language from 2008 to 2011. On 1 October 2012, Lloyd Jones was appointed a Lord Justice of Appeal, and was appointed to the Privy Council on 7 November 2012.