Olympic champion Ariarne Titmus was fastest in the 200m freestyle heats at Australia’s Olympic trials on Wednesday, setting up a showdown with world record holder Mollie O’Callaghan in the evening session’s final. Titmus won her heat in one minute and 55.50 seconds at the Brisbane Aquatic Centre, with O’Callaghan claiming hers in 1:55.68. Both swimmers have dazzled at the trials this week, with Titmus threatening her 400m freestyle world record on the opening night and O’Callaghan confirming herself as a medal contender in the 100m backstroke on Tuesday. Wednesday’s final offers a rematch of the Fukuoka World Championships event where O’Callaghan swam her world record 1:52.85 to upset Titmus for the 200m title. “People think that it´s probably just going to be Mollie and I out the front but I think the entire field is going to be competitive because it´s a very high chance that´s a gold medal possibility with that relay team,” Titmus, who is also the Olympic 400m freestyle champion, told Australian media. Lani Pallister, who joined Titmus in qualifying for the 400m freestyle at Paris, was third quickest in the 200m heats on Wednesday, ahead of Jamie Perkins, Brianna Throssell and Shayna Jack.