WilliamMontgomery represents Sotheby's on the island of Ireland. He advises clients on the purchase and sale of historic and architecturally-important properties in Ireland, the UK and Europe.  He is a member of the Arts Council of Northern Ireland and a  Trustee of The Gibson Trust, the Church of Ireland, the Ulster Historical Foundation, and the Museums and Galleries of Northern Ireland. He was Governor of the Linen Hall Library, Belfast and past Director and then Chairman of Opera Northern Ireland.