From 1960-1967, Mercer was educated at Dynevor School, at the time a state grammar school known as Dynevor Secondary Grammar School, in Swansea in South Wales, followed by the in the city of Nottingham in central England. He played most sports at school and university, and won the Welsh Junior Doubles at tennis in 1968. In 1969 he was captain of the Nottingham University tennis team
He graduated in 1970 and qualified as a solicitor in 1973.
Mercer ran his own firm in Swansea for nine years. He became a freelance sports reporter after winning a competition organised by British Broadcasting Corporation Wales in 1979, for a time combining this with his legal practice and with public relations duties for the Law Society. He has commentated on tennis including Wimbledon and other sports including soccer, rowing, skiing and American football.
Besides the British Broadcasting Corporation, he has worked for other television channels, including Eurosport.
Mercer also played racquet sports, rugby, soccer and cricket. He now plays golf. Personal life.
