Around half hour into the third day's play, Travis Head was having a chat with Chris Gaffaney. The Australian opener was busy giving the umpire from New Zealand a lowdown of last summer's Test here at the SCG, as picked up over stump mic. About how the pitch had more grass on it and about how the contest had a bit more intensity in it, with the Border-Gavaskar Trophy still up for grabs going into the final Test. Head's conversation on Tuesday came in the backdrop of the more temperate energy around the scenes playing at the SCG at this point in the summer with the Ashes already sealed.

Head was in his 120s then, looking in total command of proceedings and the English challenge. He was walking his runs. He was walking across his stumps. He was walking at the bowlers. He was simply having a blast. So much so that he had the temerity to distract himself with some chit chat with the umpire. And why not.

For the third time in the summer, Head had after all put England to the sword in such brutal fashion that he'd dictated the terms and the tempo of the contest. While rendering Ben Stokes and his bowlers rather helpless in their quest to stop him.

If the South Australian left-hander's brutality in the form of 163 In 166 balls is what set Australia apart at the SCG halfway through the New Year's Test, it was Steve Smith's mastery on a slowly deteriorating pitch that helped the hosts surge ahead into a position of complete dominance with two days left in the series.

Unlike Head, Steve Smith spent most of his time in the middle talking to himself. As is the case with him during most of his stays in the middle. Especially when he's in that very Steve Smith zone of complete control. Over how the Test match is going, and over the kind of say he's having on it.

It was trademark Smith in every way possible. Him at his eccentric best, with all the tics and the idiosyncrasies tuned up to 10. It's generally a sign of two things in Smith's world. That he thinks the surface or the pitch are a tad challenging or when he feels he's in cruise mode and needs his fidgety mind to keep him in check.

If Smith wasn't flashing thumbs up signs at the bowlers, he was yelling out "in ducker" every time one of them bowled a delivery that jagged back into him. And there were also the dozens of times he got distracted by people behind the sight-screen.

He was also playing some audacious shots, at least once he was past his 50s and eventually stitching together vital partnerships that have taken Australia well in front and in line to finish 4-1.

It was an innings where he also became the second highest run-getter in Ashes history, and with his eyes set on turning this into a much bigger score come Wednesday.

As far as England went, it was probably a day when their wheels finally began to come off. The bowling was overall ordinary with their catching even worse.

Will Jacks dropped an absolute sitter at the deep backward square leg fence, before he put one down off Head with his own bowling. Then came the difficult opportunity spilled by Zak Crawley at leg-gully off Smith. It was very similar to the catch Smith and Marnus Labuschagne had taken at vital moments in Test matches earlier in the series.

This was a great example of just how England have been unable to seize moments, forget creating them. Unlike Australia, who have on the field, in particular, both created and then seized these moments. And who now look to see their way home to a commanding final Ashes win.