Tiwai Point smelter boss standing down to take new job at Mercury Energy 6 May, 2021 09:56 PM 3 minutes to read Stew Hamilton, chief executive of New Zealand Aluminium Smelters, is leading the company to join Mercury Energy. Photo / Gregor Richardson Stew Hamilton, chief executive of New Zealand Aluminium Smelters, is leading the company to join Mercury Energy. Photo / Gregor Richardson The long-time boss of the Tiwai Point aluminium smelter, whose final years were defined by the company's threat to abruptly close, is leaving for a new job at Mercury, one of New Zealand's largest electricity companies. Stew Hamilton, who has been chief executive and general manager of New Zealand's Aluminium Smelter (NZAS) since 2018, is leaving the company to become general manager of generation at Mercury.