Lord Dyson joined Keating Chambers in 1969 where he rapidly established a wide and varied practice including appearance in the House of Lords in the leading conflict of laws case, Boys v Chaplin [1971] AC 356. Subsequent appearances in the House of Lords included Peabody v Parkinson [1985] AC 210 and St Martins v McAlpine [1994] 1 AC 85. He took Silk in 1982. In 1986 he accepted an invitation to become Head of Chambers at 39 Essex Street.
As Sir John Dyson he joined the High Court Bench in 1993; he was Presiding Judge of the Technology and Construction Court 1998-2001; he was appointed a Lord Justice of Appeal 2001; he became Deputy Head of Civil Justice 2003-2006 and was appointed a Justice of the Supreme Court in April 2010. He was the first Justice of the Supreme Court not to be appointed a life peer, but was accorded the courtesy title Lord Dyson along with all subsequent appointments to the Court.