The Sussex wicketkeeper became the third centurion of the burgeoning England first innings with a thumping hundred off just 109 balls to rub further salt into Australia's wounds. England, who last week retained the Ashes in the fourth Melbourne Test, are chasing their first series win in Australia for 24 years, while the home side, under acting captain Michael Clarke, are only looking at survival after another session of carnage. At drinks in the extended morning session, England were 584 for seven with Prior on 111 and Tim Bresnan on 35. That represented a mounting lead of 304 runs with three wickets intact and little sign that the Australian bowlers could contain it. Prior, who was 54 overnight, took to the Australian attack and raised his fourth Test century with a four through the covers off spinner Michael Beer. His 197-minute blitz was the fastest England Ashes century since Ian Botham in 1981. Prior joined other century-makers, Alastair Cook (189) and Ian Bell (115) in the England innings. It was also the fourth time England have passed 500 in the series. England's continuing domination came on a day when Paul Collingwood announced his retirement from Tests. Collingwood's announcement comes in the midst of a poor Ashes series, scoring just 83 runs from six innings at the number five batting position. The England and Wales Cricket Board said Collingwood, 34, would remain as England's Twenty20 captain and play for England's one-day team. "I'm proud of the fact that I've always given my all for the England Test team," he said. "But I feel that this is the right time to leave Test cricket having reached some very special achievements, none more satisfying that retaining the Ashes in Australia."