Jonathan Jurejko
BBC Sport in Melbourne

Just as the third set had dropped into a bit of a lull, the appearance of a protester changed the energy.

The woman was stood in the front row behind the baseline where Zverev was receiving and started shovelling pieces of paper out of a bag.

It was unclear what the protest was about.

With no security to be seen, a pair of spectators hoyed the protester up the stairs and out.

When they returned to their seats, the rest of the Melbourne crowd gave them the biggest round of applause of the match.

That's a good hold for Cameron Norrie, who saved a break point before play was halted for a bit when a protester threw bits of paper on to the court.

But Norrie keeps his composure when play resumed to get the hold.

The bits of paper that were thrown on to court were quickly cleared up and we're good to go again.

We have a protester throwing bits of paper on to the court at one end. So a bit of a hold up here.

They didn't get on to the court, just throwing it from the front row of the seats.

Zverev has a break point and if he takes it will be serving for the third set. He has won three of the past nine break points.

A fist pump from Zverev as he backs up the break in routine style with a hold to love. This has been some response from the sixth seed and he's now in total control of this set.

Jonathan Jurejko
BBC Sport in Melbourne

The Cameron Norrie Supporters Club (Melbourne Branch) are trying their best to lift their man.

Two young lads have been vocal throughout the match, shouting out encouragement to 'Noz' and trying to instigate chants.

One is wearing an 'N' on the front of his white tee. The other is wearing a 'Z' on his.

Where the 'O' is we don't know.

Unless they're from New Zealand...

A very loose game from Norrie. He can only send a forehand halfway up the net and Zverev gets the break.

Being broken in the second set then spurred Norrie on to his best tennis of the match so can he do the same again here?

Cameron Norrie punches a volley long at the net and it is three break points for the German, 0-40.

We're back to the first set where the pair were swapping routine holds. Zverev gets the job done with a two-handed passing backhand from the baseline as Norrie moved forwards for a hold to 15.

Norrie is straight back on it though with a hold to 15. Zverev tries a drop shot, but it sits up nicely for Norrie, coming forwards and crouching, and he is able to flick a winner down the line. One set apiece, one game apiece in the third.

An ace, his sixth of the day, from Zverev helps him win his first game in more than half an hour as he makes a clean start to the third set.

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Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra and BBC Sounds

We are starting to see a few more miss-hits, shanks. The tension is growing for Zverev.

Have a look where Zverev is playing from – it is so defensive.

And it is nice to see Cam still persevering in moving forward.

Image source, Getty Images

We're level.

Cameron Norrie was a break down at 3-2, but does superbly to win four games in a row to take the second set.

He gets a slice of luck with the last shot of the set as the ball bounces off the net, loses all its pace and drops the other side.

It is the first time Norrie has ever taken a set against Zverev.

Norrie has saved four break points in this game. Now, for a second time, has a set point.

Three break points Norrie has now saved, but he will have to do it again after pushing a two-handed down-the-line attempt wide.

Two-time finalist Daniil Medvedev has got the double break in the fourth set and will serve for a place in the quarter-finals.

Portugal's Nuno Borges had a game point but a flurry of errors, including two easy volleys at the net, have left him on the brink.