text: Costello is the only leader of an Irish political party killed to date.
  At the time of his death, he was a member of the following bodies:
  Wicklow County Council
  County Wicklow Committee of Agriculture
  General Council of Committees of Agriculture
  Eastern Regional Development Organisation
  National Museum Development Committee
  Bray Urban District Council
  Bray Branch of the Irish Transport and General Workers Union
  Bray and District Trade Unions Council (of which he was president 1976–77)
  Cualann Historical Society
  as well as still holding the positions of
  Chairperson of the IRSP and
  Chief of Staff of the INLA.
  His funeral was attended by Ruairí Ó Brádaigh, the then president of Sinn Féin, Michael O'Riordan of the Communist Party of Ireland, Bernadette McAliskey and local Wicklow TDs Liam Kavanagh (Labour), Ciarán Murphy (Fianna Fáil) and Godfrey Timmins (Fine Gael). At his funeral, former Senator Nora Connolly O'Brien, daughter of the Easter Rising leader James Connolly, gave the oration.
  Of all the politicians and political people with whom I have had conversations and who called themselves followers of Connolly, he was the only one who truly understood what James Connolly meant when he spoke of his vision of the freedom of the Irish people.