American star Katie Ledecky was fastest in the heats for the Olympic women’s 400 metres freestyle ahead of the final later on Saturday. Ledecky, a seven-times Olympic gold medallist, won this event 2016 in Rio but only managed silver three years ago in Tokyo when she was edged out by Australian world record holder Ariarne Titmus. She turned the tables in the Paris heats, finishing 0.27 seconds ahead of Titmus in the same heat, with New Zealand’s Erika Fairweather third quickest overall and Canadian Summer McIntosh fourth. Ledecky said: “I was trying to have a good swim and get into that final …