The first two and a half days left hardly an inch between the teams but a gutsy stand between Ian Bell and Broad was gradually turning the tide in the home side's favour, seeing them to 297 for six.
As on so many occasions in this match Australia hit back at a crucial time, with Broad on 37 not out and the lead at 232.
Broad got a thick outside edge to an Ashton Agar delivery and the ball was smartly held by Australia captain Michael Clarke via a ricochet off wicketkeeper Brad Haddin.
Broad declined to walk - unusual for so clear an edge - but the real shock was when umpire Aleem Dar ruled him not out.
Australia would have easily overturned the verdict with a DRS review but they had already used their allocation of two on failed lbw calls against Joe Root and Jonny Bairstow.
Former England all-rounder Dominic Cork told Sky Sports News: "Have you known any Australian to walk when he nicks it? Michael Clarke and the Australians having a go at Stuart Broad? Seriously Australia - it's sour tactics.
"They didn't worry about Jonathan Trott yesterday [Thursday]...they can't have one rule for one and one for another. I've played with Australians who would nick it to second slip and think they could stand there.
"It's international cricket. Get on with it.
"What makes me laugh is Australia standing on that pitch (slating Broad) for not walking. They've done it for about 50 years. Adam Gilchrist is the only player I know who'd walk when he'd nicked it.
"The right decisions are being made, 98, 99 per cent of the time - and that's all you want. As long as technology is used and you say to the players 'we can't guarantee 100 per cent accuracy' they'll be happy with that.
"There's always the one per cent when Hotspot doesn't pick up a little nick. It might be something that goes in the favour of whatever team.
"But the issue is technology. Use it and enhance it. Keep with it, stick with it, have faith with it. It works."
Shane Warne, Australia's all-time record wicket-taker in Tests, was not surprised by the decision.
He wrote on his Twitter page: "No surprise re Aleem Dar. He's always had no idea.."
Reviewing the incident on Sky Sports Ashes, former England captain Andrew Strauss said: "I think it's one of the conventions in the game that you can get away with, very few would do."
Strauss added that Australia could have saved their earlier reviews, though.
"The review system is in place to get rid of the howler, but Australia used theirs' on touch-and-go decisions," he said.
Former West Indies bowler Michael Holding brought up countryman Dinesh Ramdin being suspended by the ICC for claiming a catch he had dropped.
"Broad played the ball and stood there, he has done the same thing, is that not contrary to the spirit of the game?" he asked.
"I am worried that the ICC have opened up a very dicey situation. What Stuart Broad did and a lot of others is also contrary to the spirit of the game."
England batsman Kevin Pietersen said: "Every batsman around the world has to wait for the umpire's decision.
"Aleem Dar has been rated one of best umpires and he (Broad) is well within his right's to wait for the decision."
Strauss also touched on the last series in Australia when current Baggy Green captain Michael Clarke was given not out caught on the last ball of the day at Adelaide.
Clarke later apologised for not walking after he was given out on review.
"Fortunately we had another review left, we took it and it was given out. A thick edge was not given out," Strauss recalled.
Former England captain Michael Vaughan said: "The review system was brought in to get rid of the howler.
"I don't see why Dar couldn't have had someone is his ear saying 'you've got that one wrong, let's just overturn that quickly'.
"This has been a terrific game but I think a lot will be talked about that incident, which is sad."
Former Australia pace bowler Glenn McGrath added on the BBC Sport website: "DRS was brought in to correct obviously wrong decisions and that is how captains should use it.
"Alastair Cook does just that, he is very sparing with it, and hopefully Michael Clarke does the same after this."
Warne was not as forgiving as his old team-mate, though, and continued to berate Dar.
"We all make mistakes & it's a very tough job being an umpire, but when Dar continually makes crucial mistakes why does he keep getting a gig," he tweeted.