He was a member of
Dublin County Council from 1985 to 1993 and was a member of
Dún Laoghaire–Rathdown County Council from 1994 to 2002. He was first elected to
Seanad Éireann in 1987 and was elected at all subsequent elections until his defeat at the 2007 election. He has at various times been the Senior Senate Spokesman on Justice, Senior Senate Spokesman on the Department of the
Taoiseach and European Affairs, Senior Senate Spokesman on European Affairs, and laterally held the position of Spokesman on Foreign Affairs with Special Responsibility for Overseas Development Assistance and Human Rights. He has served as a member of the Joint Parliamentary Committee on Women's Rights, the Joint Services Committee, the Joint Parliamentary Committee on Social, Community and Family Affairs and was laterally a member of the Joint Parliamentary European Affairs Committee. In February 1993, during a meeting in the council chamber of Dublin Corporation, he famously grabbed the
Green Party TD
Trevor Sargent in a headlock when Sargent waved a cheque, sent to him by a builder. Sargent asked the rest of the council had they been sent any checks, and if they thought that this was a case of the building sector attempting to bribe the council. Lydon was nominated as a candidate for the 23rd Seanad in 2007 and stood as a member of Fianna Fáil. His proposers included Senator
Tom Morrissey, former Fianna Fáil Senator
Margaret Cox and Fianna Fáil TD
Ned O'Keeffe. He lost his Seanad seat in the 2007 election. He was a member of the Irish Council of the European Movement and served as vice-chairman from 1991 to 1993. He was also a member of both the Council and Executive of The Institute of European Affairs. ==Bribery investigation==