The London Games officially opened on July 29, 1948. From the Wikipedia entry for the 1948 Summer Games: "The Games opened on 29 July, a brilliantly sunny day. Army bands began playing at 2 pm for the 85,000 spectators in Wembley Stadium. The international and national organisers arrived at 2.35 pm and George VI and Queen Elizabeth, with Queen Mary and other members of the Royal Family, at 2.45 pm. Fifteen minutes later the competitors entered the stadium in a procession that took 50 minutes."