William Leary studied at the Royal Mancheter College of Music from the age of fifteen, later studying with Frederick Grinke in London. At the age of eighteen, he joined the Royal Liverpool Philharmonic Orchestra where he was later appointed Co-Leader, a position he held until 1970. He went on to join the London Philharmonic Orchestra as Sub-Principal first violin, recording and touring extensively, playing under conductors such as Bernard Haitink, Carlo Maria Guilini, Georg Solti, Lorin Maazel and Daniel Barenboim, and fulfilling engagements during the summer months at Glydebourne.
William left the London Philharmonic to return to the North of England where he freelanced with the BBC Philharmonic in Manchester and Opera North, Leeds.He also indertook several international tours with London chamber ensembles. William was appointed as Head of strings at Ampleforth College, North Yorkshire where he remained until December 2003. He joined the staff at the University of York in January 2004.