SYDNEY - Olympic swimming great Grant Hackett is back in full-time training and could compete in Australia’s national championships in April as he pursues his comeback following a troubled spell in retirement. Hackett, 34, quit professional swimming in 2008 after winning the 1,500m freestyle at both the 2000 and 2004 Olympics, and claiming four world titles in the event. But his life later spiralled out of control, including allegations he smashed up his Melbourne apartment and a messy divorce from singer-songwriter wife Candice Alley. Earlier this year the former 1,500m world record-holder underwent rehab in the United States after seeking help for an addiction to sleeping pills. He is now back under his old coach Denis Cotterell and training six days a week.