Tiki Gelana of Ethiopia made her move with less than two kilometres left to capture Olympic women's marathon gold in Games record time on a wet Sunday in London.
Gelana, 24, ran away from three rivals, including Kenyan pre-race favourite and two-times London marathon winner Mary Keitany, to win in two hours 23 minutes and seven seconds.
Riscah Jeptoo of Kenya got silver as at the 2011 world championships, and Russian 2007 world championship steeplechase silver medallist Tatyana Arkhipova took bronze, leaving no place on the podium for Keitany.
Lisa Weightman was the leading Australian in 17th place - only the third Australian woman ever to manage a top 20 result in the event.
Gelana's previous claim to fame was victory in the 2012 Rotterdam marathon, with her winning time of 2:18:58 there fifth in the all-time list.
With local hope and world record holder Paula Radcliffe missing injured, the race started amid a torrential downpour after a thunderstorm and ended in driving rain as well.
The course did not follow the route of the annual London marathon but had one short and three longer laps to take in famous landmarks such as Big Ben, Tower of London, Trafalgar Square and House of Parliament.