That's all from this live text - thanks for reading. We'll be back for day four at around 23:00 GMT. But there is plenty more to keep you occupied until then...

The day three report is available here.

Listen to and download the Test Match Special podcast here, while there are also currently highlights over on BBC Radio 5 live sports extra.

Pint-Sized TMS is available here.

And it's not pretty viewing for England fans, but here's the scorecard.

Cheers!

Ed Smith
Ex-England batsman on BBC Test Match Special

The best thing that can happen to the Ashes is more even matches.

Shaun Marsh looks well set to join Khawaja in the century club this Test when he resumes on 98 tomorrow.

And Mitchell Marsh will also be hoping to join him as he plays the aggressor, starting on 63 not out.

That would make it four centuries for the Marsh brothers in the series. Australia's selectors definitely beating their England counterparts.

All in all, an extremely tough day for the tourists, underlining the disparity between these teams in these conditions.

Australia batsman Usman Khawaja, who made 171, on ABC: "It was a tough day but ended up being a very good day.

"With the wicket wearing up, we wanted to get as many runs as we could. We knew first-innings runs were important.

"I grew up playing at the SCG - and a first Ashes hundred... It felt really far away before the start of the game. I wanted to get a big score. It's amazing how things can change."

So day three belongs to Australia and in no small part that is due to Usman Khawaja, who secured his first Ashes century and kicked on delightfully from there.

Using his feet well to the spinners, deftly whipping off his hips and driving through the covers, it was a wonderful and watchable knock.

He ended with 171 on his home ground, answering his doubters after a poor series. And here's what he had to say afterwards...

Francis Edwards: There isn't anything wrong with the pitches in Australia, what's wrong is England's low 80mph bowlers expecting to succeed on wickets that aren't green tops.

Image source, Getty Images

England will return on day four, hoping desperately for some early wickets to at least halt Australia's charge.

And they are due to get another new ball after three overs tomorrow.

The third new ball - surely one of the most depressing moments for a bowling side.

Graeme Swann
Ex-England spinner on BBC Test Match Special

I can see England drawing this Test, but I can't see them winning it. The problem will come with Nathan Lyon, who won't bowl as many bad balls as the England spinners. I'd be tempted to break up the batting order. Be ultra aggressive to him - he doesn't like it.

In reality, that 1% seems generous.

Australia will look to add more runs to their lead in the first session of day four, potentially setting up a declaration around lunch.

They may even decide to bat beyond to ensure they only bat once in this Test and try to skittle England cheaply for an innings victory.

Can England escape with a draw at Sydney and 'only' lose the series 3-0?

Don't give up hope just yet, according to Cricviz there's still a 1% chance England can win this Test...

Image source, .

Graeme Swann
Ex-England spinner on BBC Test Match Special

It was a very good stumping by Jonny Bairstow, who has had a superb Ashes with the gloves. His wicket-keeping has been just wonderful to watch. Ones that come back between bat and pad, with a moving batsmen, are difficult, but Bairstow took it with aplomb.

And now for the wickets...only two of them to write about...

Moeen Ali, bowling with a bit more accuracy but still without regular menace, removed Steve Smith with one that bit, the Aussie skipper miscuing his drive and returning a catch to the England all-rounder.

Mason Crane then got his first Test wicket by spotting Usman Khawaja on the charge, tossing it up wide and spinning it through bad and pad, with Jonny Bairstow completing the stumping.

Huge relief for the 20-year-old, not least because he was denied the wicket of Khawaja earlier after he overstepped. England had reviewed and the lbw decision would've been overturned save for the no-ball.

Image source, Getty Images

Bobby, Lancashire

Hello to all of you just joining us. It's been a brutal day in the field for England as Australia have added 286 runs for the loss of just two wickets.

Let's start with the runs - 80 off them came from the bat of Usman Khawaja, who converted his 91 not out overnight into a sublime 171.

Steve Smith moved towards what looked like an inevitable fourth century of the series, only to be caught and bowled by Moeen Ali for 83.

Yet still the Aussies kept coming, now in the shape of the Marsh brothers. Shaun is unbeaten on 98, with Mitchell 63 not out. Australia have closed on 479-4, a lead of 133.

Image source, Getty Images

John in Bucks

There was evidence of turn at Sydney throughout day three.

Joe Root got one to rip past the edge of Shaun Marsh's bat - it was given out caught behind but Marsh reviewed successfully, with DRS showing he didn't edge it.

Mason Crane also tore a few past the outside edge of Mitchell Marsh - the young leggie looking better bowling to right-handers.

And Moeen Ali finally found some bite to remove Steve Smith, inducing a miscue that ended up back in the hands of the bowler.

The SCG is not Dhaka though and, once in, Australia's batsmen have been able to repel England's spin attack.

Shaf from Bedford

Mason Crane did think he'd got his first Test wicket before lunch - England reviewing an lbw decision of not out against Usman Khawaja.

Ball tracking showed it was hitting the stumps and would've been overturned, but the third umpire judged the young leg-spinner had overtstepped.

It wasn't entirely clear if any part of his boot was behind the line - a tight one that people will have differing interpretations of.

David Thackeray: Bairstow giving the bowlers plenty of praise. Somebody remind him that Australia are 479 for 4. Oh, and we need men - not boys.

With temperatures reaching the mid 30s, the SCG was also bathed in the hot pink of the McGrath Foundation, a breast cancer charity founded by former Australia fast bowler Glenn McGrath in memory of his late wife Jane.

Khawaja and Smith were unfazed by the heat, seeing off the new ball and accumulating steadily, with Khawaja also bringing up his first Ashes hundred.

England's spinners bowled well, but without constant menace, while it was yet more toil for the seamers on a very good pitch for batting.

The shock wicket of Smith the only thing to energise England before lunch, which Australia reached at 277-3.