After a catastrophic day for the tourists on Sunday, when England conceded a big lead to the Australians, things got even worse for them on day four.
The Australian batsmen put them to the sword before lunch, and the home team then made immediate inroads into the England batting line-up in their second innings.
At tea England were 95 for three, with Kevin Pietersen on 21 and Ian Bell on six, the pair probably England's last chance of saving the match and staying in the series.
Australia will claim the five-Test series with a win in Perth, having won the first two Tests in Brisbane and Adelaide.
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England's second innings got off to a disastrous start when captain Alastair Cook fell for a golden duck, the first of his 100-Test career, from the first ball of the innings.
Cook was clean-bowled by Ryan Harris, becoming the first player to suffer the ignominy of a first-ball duck in their centenary match.
Root called for a review, but it showed a clear edge through to wicketkeeper Brad Haddin, who took a fine diving catch.
Australia declared their second innings at 369-6 after fireworks from Watson, who took just 40 balls to race from his overnight score of 29 to his fourth Test century, and George Bailey, who equalled Brian Lara's Test record with 28 runs off one Jimmy Anderson over.
Possibly the only good news for England was that Broad was cleared of a serious foot injury and could still play in the last two Tests of the series.