 He helped to establish the chair of architecture at the University of Sydney and to secure the recognition of public competition for public buildings.John Hennessy was in partnership with Joseph Sheerin as Sheerin & Hennessy from 1884 until Sheerin left the partnership in 1912.Both were devout Catholics, active in Church charities, and were friends of Archbishop (Cardinal) Moran, and were commissioned for a number of large projects for the church, including two large colleges and the Cathedral of St Mary and St Joseph in Armidale, in country NSW.