John 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  AC 356. Subsequent appearances in the House of Lords included Peabody v Parkinson  AC 210 and St Martins v McAlpine  1 AC 85. He took Silk in 1982. In 1986, he accepted an invitation to become Head of Chambers at 39 Essex Street.
John Dyson was appointed to the High Court Bench in 1993; was Presiding Judge (Technology and Construction Court) 1998-2001; Lord Justice of Appeal 2001; Deputy Head of Civil Justice 2003-2006 and was appointed a Justice of the Supreme Court as Lord Dyson in April 2010. In September 2012 he was appointed, in succession to Lord Neuburger, as Master of the Rolls.