Question: What was this major international multi-sport event, with the opening ceremonies taking place on 27 July, and in which the South African field hockey player Bernadette Coston competed for the outh Africa women's national field hockey team?
Sentence (from "2012 Summer Olympics"): The first event, the group stage in women's football began on 25 July at the Millennium Stadium in Cardiff, followed by the opening ceremonies on 27 July.
Relevant evidence: No