Murray takes too long to hit a lob and Zverev smashes it back past him. Another forehand goes awry from Murray then a sterling serve from Zverev, pacey and right into the corner, foxes him.

Ace! Zverev has taken the first set! This has been engrossing tennis. Game on.

Zverev has broken Murray three times now. It's getting hotter out there too. This will be a test of fitness and a test of mental strength as well. Who can hold out the longest?

Down the line forehand again from Zverev, overhit again by Murray who is looking less and less thrilled by the second. He comes up to the net and goes big on the backhand, thwacking it beyond Zverev.

Break point comes as Murray loses his line and that is superb from Zverev! Back up at that net, the tiniest of flicks over and Murray was too far back to get near it. Brilliant tennis from both men, but it's Zverev serving for the first set.

Russell Fuller
BBC tennis correspondent on Radio 5 live sports extra

What a fabulous start by Zverev: it's great to see someone serve and volley so regularly and some of his returns have been astonishing. He remains a very clear second favourite to the win the match, but he deserves a major stage to show off his talents after battling back from a catalogue of injuries which saw him drop out of the world's top one thousand.

Image source, BBC Sport

Zverev is up at the net, he's cramped for room but his backhand is superb. It's dinky and well-timed and Murray goes for his get out shot, the lob, but it's out.

That's a speedy hold for Zverev. Murray is in need of a rethink.

* denotes next server

Nice return down the line from Zverev, which Murray challenges to no avail, before the Brit slices his forehand into the net.

He's chuntering furiously to himself now but it's Zverev who blinks first, his backhand sailing wide. Murray's forehand is wide though, and that's break point. 

Lendl is leaning forward, eyes fixed on the game, but it's Zverev that breaks as Murray misses his backhand! 

5 live's Cat Archer: "Fans blowing out cool, wet air....and it feels great. 30 degrees and counting at Melbourne Park."

Image source, bbc

Murray wins the rally at the net this time, floating up his forehand and Zverev's leaping dive can't get to it. 

There's then a yell and some words I couldn't possibly repeat from Murray as he tamely returns his forehand into the net. Every time it swings towards Murray, Zverev will trick him with that backhand.

A double fault gives Murray a break point before Zverev, up at the net again, slices his backhand into it. He's kicking himself for that.

Three times Murray has had the advantage now, all from Zverev overhitting, and he makes it count this time. A backhand close at the net secures it. 

He will hold, and he's straight off for a sit down under the natty shaded seats the Rod Laver Arena has.

Zverev gets to two break points with a gorgeous drop shot that wrong foots Murray completely.

He's annoyed with himself and he throws more power into his forehand to save one. His backhand is superb too, spin and pace, and Zverev waits too long to return it. Deuce.

Murray gets the advantage but Zverev is a superb mover. Murray is up at the net, looks to have dropped it too short to reach, but the German scampers over and hoofs it past him.

Right then. After that long game Zverev powers to 40-0, Murray's backhand twice going awry, before a forehand winner gets him on the board.

Both men go for an big ol' smash but Zverev's isn't as well-timed. Murray overhits his next attempt though, and that's that. All square.

Honestly. Daft. Murray goes for overhead after overhead. He's so far back he's in the shade of the court and they're all landing it. But a backhand on one goes too far and he loses his advantage.

Zverev comes forward to the net, tipping over for a break point - and he's done it! A backhand winner and a clench of the fist. He's broken straight back.

Ooft! A stunning rally from these two. It's all very simple, backhand to backhand, before they gradually come forward.

Zverev goes for the overhead, Murray backpedals and returns from the shade. Zverev goes for a flick and takes the point! Murray was 40-0 and that takes it to deuce.

The battles at the net have the crowd making all sorts of noises and Zverev wins it again for a break point, but a Murray ace sorts that out.

Sharon Camley: 2nd early rise in couple days can only mean one thing - lets go Andy, lets go.....

Gemma-Lou: Early riser, will be up for Evans too if I can stay awake.

Ahmed Osman: Hoping for a comfortable three set victory, lets go Andy!

If you're up already then you are ahead of the game, but let's mark your card for how to follow the action over the next 8, 9, 10 hours.... who knows?

Commentary is up and running on 5 live sports extra, which you can access through the top of this page, and they will be going right through to cover Evans v Tsonga.

If that's not enough, you can catch up with the highlights of Sunday's action on BBC Two at 17:15 GMT.

Be a good one, this, as Zverev wins another rally at the net with a backhand volley. Murray responds with a furious ace.

Lovely from Murray, putting plenty of spin on the ball as he goes short, but Zverev puts him under pressure in the rally. Sliced backhands galore and it's Murray that ends up overhitting.

Up to the net again and Zverev somehow backpedals and goes up and over. Deuce. A casual 131mph serve gives Murray the advantage, and another ace gives him the game.

Image source, Getty Images

John-Laffnie de Jager, Heather Watson’s coach, on 5 live sports extra: “The first serve for Zverev is key, sometimes it’s not about the pace but the variety you can throw in, sliding the ball out wide or into the body. He needs to be above 65% for first serves to have any business in this match.”

Zverev's first serve is right in Murray's area and the Brit says thank you very much and smashes it back past.

If they keep leaping about like this they'll be exhausted, given the heat. Murray miscues three backhands in a row, struggling to pick up that serve, but a lovely lob lands in for deuce.

Zverev's forehand is off, giving Murray the advantage, but a hearty thwack at the net saves him. Murray backhands into the net before a classy forehand means Zverev holds.

There's a bit of sighting each other out before both players end up at the net. It's a tight rally, Zverev sprawling to dink a backhand over, but Murray is crafty and hammers a forehand beyond his reach.

Another long rally, Zverev's backhand looking strong, and it's Murray who slashes the ball into the net. However the German mistimes his backhand and Murray holds his serve.

* denotes next server

Image source, Getty Images

Mischa's younger brother Alex is in the box, fist pumping and suitably embarrassing his brother.

Here we go  - Murray will serve first.