Jonny Bairstow's brilliant day at the SCG was tainted by a row with a spectator who abused him as he and Ben Stokes headed for the pavilion at the tea interval.
England had slipped to 36-4 at lunch after a delayed opening session, before Bairstow and Stokes carried the fightback, putting on 128 for the fifth wicket before the latter was trapped LBW by Nathan Lyon for 66.
Bairstow continued his counter attack though, cutting Pat Cummins to the fence in the final over of the day to reach 103 not out, with England heading into day four on 258-7 in reply to Australia's 416-8.
It was the Yorkshireman's second Ashes ton and first at Test level since 2018, but his day was somewhat marred after being involved in a flash point as he and Stokes left the field following a wicketless second session.
In a video published by the Sydney Morning Herald, one spectator can be heard shouting "Stokes, you're fat," before another chirps in with "Take your jumper off, Bairstow. Lose some weight, Bairstow."
Stokes, who appeared to be battling injury throughout his knock, and Bairstow suddenly stopped at the top of the stairs before the latter fired back with "Pal - that's right. Just turn around and walk away. Weak as p***."
Surrounding fans did instead opt to applaud the two batsman, while England's managing director Ashley Giles soon appeared to embrace Bairstow - whose knock included eight fours and three maximums.
Despite the fourth Test essentially being a dead rubber, there was no shortage of needle at the SCG as the hosts push for a whitewash.
The England centurion later told reporters the perpetrator had disappeared when he walked off at the close.
"It was a bit of bad mouthing from the crowd. It's not the greatest and it's not needed," he said.
"We're out there trying to do our jobs and people are enjoying the day's cricket but unfortunately sometimes you have people who overstep the mark.
"I think it's important to stand up for ourselves because if we don't we can cop it if people overstep the mark they need to be told. It would have been nice if they had still been there giving it to us when we walked off at the end."
Bairstow and tail ender Jack Leach will resume proceedings overnight, as the tourists seek to eat in to their current 158 run deficit.
