He now received more substantial commissions, two of them the greatest undertakings attempted in New Zealand up till then: the building for the New Zealand Exhibition and a new post office for the Otago provincial government. The first was completed in 1865 the second in 1868. The exhibition building had been conceived with additional pavilions, evident in a water colour by the artist George O'Brien. O'Brien also depicted the new post office, a structure so grand that before its completion it was decided it needed a higher purpose.