TOKYO, July 29 (Reuters) - Emma McKeon can add to Australia"s golden haul in a women"s 100m freestyle final packed with champions and record holders at the Tokyo Olympics on Friday. After smashing the Olympic record in the preliminary heats with a personal best of 52.13 seconds, McKeon starts in lane four in pursuit of her fourth medal of the Games. Hong Kong"s 200m freestyle silver medallist Siobhan Haughey could be McKeon"s closest challenger, followed by Australia"s former world champion and triple Olympic relay gold medallist Cate Campbell. The field also features Canada"s defending Olympic champion Penny Oleksiak, Sweden"s world record holder Sarah Sjostrom and 2016 medley relay gold medallist Abbey Weitzeil of the United States. Australia have so far won five golds in the swimming, four provided by women, but McKeon has yet to win an individual title. "She’s in good form," Australia"s five-times gold medallist Ian Thorpe told Seven television. "But, of course, she’s up against Cate Campbell and the likes of the best competitors in the world. "So that one’s a tough one to call, but I think she will medal in that." South Africa"s Tatjana Schoenmaker has the world record in her sights in the women"s 200m breaststroke after qualifying close to the mark. "I wish had longer fingernails," she told reporters after missing it by five hundredths of a second. Olympic 100m breaststroke champion Lilly King qualified only fifth fastest. In the men"s 200m backstroke, Luke Greenbank was second fastest to Russian favourite Evgeny Rylov in the semis as Britain enjoy their best Olympic swimming performance in 113 years. "There have been some inspiring performances and I really want to get in on that action and come away with a medal," he said. Compatriot Duncan Scott has his chance of individual gold in the men"s 200m medley, with China"s Shun Wang, Japan"s Daiya Seto and Michael Andrew of the United States his big opponents. A medal of any colour would keep Scott on course to become the first British athlete to win four at a single Games.