Bayfield was born in Bedford and was educated at Bedford School. He served in the Metropolitan Police from 1985 to 1989, when he transferred to Bedfordshire Police. The 208 cm (6 ft 10in) tall Bayfield made his England debut in 1991, and although he was omitted from the 1991 World Cup squad, was a part of the 1992 Five Nations Grand Slam winning side. He went on the 1993 British Lions tour to New Zealand and was part of the 1995 World Cup squad. He would play 18 times partnering Martin Johnson. His final appearance for England came in the 1996 Five Nations match against Wales.
His last game was against Gloucester in February 1998; a neck injury sustained in training a few days later forced him to retire.
In his broadcasting career he has presented the NFL and World's Strongest Man coverage on UK Channel Five and worked as a rugby correspondent on BBC Radio 5 Live. He has also been involved as a presenter in ITV's coverage of the 2007 and 2011 Rugby World Cups as well as presenting ITV's Guinness Premiership highlights. Since March 2012 he now also co-presents Crimewatch on BBC 1.
Since retirement, Bayfield has worked as a Journalist, an after-dinner speaker and has since appeared in all of the Harry Potter films playing the half-giant Hagrid, as Robbie Coltrane's body and stunt double. He also appeared in Harry Potter and the Chamber of Secrets, as a young Rubeus Hagrid. Continuing the acting theme, he also played a cyclops in Jonathan Liebesman's Wrath of the Titans, the sequel to 2010 movie Clash of the Titans. Bayfield also played Rugby Player 2 in an episode of New Tricks on BBC1 (first shown on 1 September 2008).
In 2013 BT Sport acquired the exclusive rights to the Aviva Premiership. Bayfield, along with his ITV co-presenter Craig Doyle, moved to the new channel and he now works as a presenter, pundit and pitchside reporter.
In August 2014, Bayfield was one of 200 public figures who were signatories to a letter to The Guardian expressing their hope that Scotland would vote to remain part of the United Kingdom in September's referendum on that issue.
