Brock had worked in Port Pirie's lead smelter, which was eventually acquired by Nyrstar, since arriving in the town in 1976. He was first elected to the Port Pirie Regional Council (at that time a City Council) in 1989, and served on numerous community committees before being elected mayor in May 2003, defeating sitting mayor Ken Madigan by 3,297 votes to 2,173. He retired from Nyrstar in September 2007, and he and his second wife Lyn have 12 grandchildren between them.
