Michael Clarke propelled his extraordinary year to new heights on Thursday, his second double century in consecutive innings against South Africa charged by his desire to “cash in” during the good times, the Australia captain told reporters. Clarke’s unbeaten 224, which drove Australia to a mammoth first-day total of 482 for five in the second test, followed his 259 not out in the drawn first test in Brisbane and made him the first player to grab four double-tons in a calendar year.