sentences:  In January 2009, a retired police detective revealed an unsuccessful attempt to derail the Royal Train near Bowenfels, New South Wales on 29 April 1970.The Queen returned to Australia again in 1973 to open the Sydney Opera House and also in 1974 to open the Australian Parliament in Canberra.This time the Queen returned to London on 28 February for a General Election in Britain, cutting short the tour, which the Duke of Edinburgh completed.