Meet the <i>other</i> Mitchell Johnson

England, we'd like to introduce you to the other Mitchell Johnson. Not the meek, erratic bowler your batsmen have enjoyed so much over the past year and a half, but the version who on his day is the most destructive in the world.

Those days have been increasingly rare lately, but during a week of intensive training in the WACA nets he rid himself of his inferior alter-ego and rediscovered his action. Today he found a way back into the series for Australia. Last week in Adelaide he was unplayable, and dropped for the first time in his Test career; this time it was England who had no idea where the ball was going.

Finally he was the bowler who could gain swing at high speed, instead of being the fragile guy England's batsmen didn't rate. They had no reason to - until today. Six wickets for 38 runs, including 4 for 7 in 27 balls before lunch, changed minds and momentum.

Johnson had made it easy for people to give up on him. No bowler has been as frustrating after promising so much against South Africa over two series in 2008-09. Having shown he could be a wrecker, he became a wreck, spraying balls, dropping his arm and doubting his method. He was so bad even the Australian selectors gave up on him. Dropping him has reignited his career, a common theme among exceptional athletes.

Sent to Perth a week ago, Johnson worked with Troy Cooley, the bowling coach, and remodelled his action successfully. He started to run in like a medium pacer instead of a sprinter, with all his energy focused on the crescendo through the crease during a huge delivery stride. It helped make his body taller, his left arm higher, and put his wrist behind the ball.

Partway through the unexpected renovation something familiar started to happen - he began to swing the ball. Like snowflakes at Christmas, everyone got really excited. The Australians became delirious when it occurred in a match and Johnson's spirit swept through a team that started to believe again.

Before the series Johnson said he wouldn't bother about swing and a match later he was out of the side. Plenty of illogical things have been said by the Australians during their extended slump, but this was among the craziest comments. When Johnson shapes the ball in he becomes a monster because the batsmen can't leave with confidence. The South Africans found that out here two years ago, when he started his summer of devastation with a spell of 5 for 2 in 21 balls that turned into 8 for 61.

This performance didn't do as much numerical damage, but it will be priceless if it turns into a victory for Australia. The morning started like the past eight of the series, with England in control and Australia fumbling. Johnson, who delivered two controlled overs late yesterday, was saved until after Ryan Harris and Ben Hilfenhaus had failed to breakthrough.

Alastair Cook has been an immoveable object for most of the series, but Johnson forced him to slice to gully, where Michael Hussey collected a smart catch. For the next four wickets Johnson didn't bother enlisting his team-mates as he delivered a series of brutal inswingers around 140kph. Jonathan Trott attempted a drive from a full ball and was caught in front when surprised by the swerve. Three balls later Kevin Pietersen, fresh from a double-century, erred in similar fashion.

Suddenly Johnson had 3 for 4 in two overs and he pumped his fist in a mixture of relief at himself and anger at his critics. No matter how high he flies, he must not forget how awful he has been over the past year and half - and how to rectify the problems when they reappear. He had to wait until the middle of a major series to do remedial work that could have been completed in the off-season or between series. It is the most stunning turnaround.

Paul Collingwood somehow survived a fierce bouncer that narrowly missed his gloves and helmet, but couldn't escape the follow-up full ball. Another late inswinger resulted in another lbw shout that was initially given not out. The Australians challenged and the replays showed Collingwood's bat stuck in its downswing about 30cm from the ball when it crashed into his pad. England were now the ones in crisis at 5 for 98 and after a nine-over spell Johnson was given a rest.

He returned almost an hour after lunch and finished off the innings when he sent Chris Tremlett's off stump cart-wheeling and watched James Anderson glide to first slip. Anderson and Johnson have been trading verbals over the past month, but during the last two days Johnson has backed up his talk. England now know all about him - and don't like him.