Blacket enlarged the building by two bays in length and added the central tower. He also proceeded to change the overall form and detailing of the building. In October 1850 six bishops of Australasia met in Sydney for a conference. Someone suggested that as there were six pillars in the nave of the cathedral each should bear the name of one of the Bishops. William Grant Broughton, Bishop of Sydney and Metropolitan; George Augustus Selwyn, Bishop of New Zealand; Francis Russell Nixon, Bishop of Tasmania; Augustus Short, Bishop of Adelaide; Charles Perry, Bishop of Melbourne and William Tyrell, Bishop of Newcastle. The pillars were so named. In 1868 the Duke of Edinburgh attended St Andrew's for an organ recital.