It certainly helps speed things up en route to your career Grand Slam if you win the opening service game to love, but after a confident start, Alcaraz is unpinned by a volley he dipped too low to catch cleanly, 30-15.

An unplayable serve is a nice chaser though, and an ace even better. A neat hold from Alcaraz.

What will Djokovic, on serve, do now?

A double fault isn't the most confident way to start off a service game, and Djokovic falls two points behind as Alcaraz unleashes a finely sliced backhand to outdo him, love-30.

Djokovic then goes for a sharply angled backhand volley, but can't pull it off over the net. That's three set points for Alcaraz.

Djokovic deals with one of them with impeccable style, quick to everything Alcaraz can throw at him before leaping for a final smash into open court, 15-40. Another falls, with Djokovic hitting confidently and forcing Alcaraz to go long.

Ace! That's pulled him up to deuce, by the finest of margins. He's saved 35 break points of his 48 at the tournament, so far.

But Alcaraz pulls off a ballerina-like curving backhand drop shot, which lands so delicately on the line, you can barely believe it.

A serve brings back deuce for Djokovic, and a hammer-heavy forehand return from him is too much for Alcaraz, handing the Serbian the advantage for now. But it's deuce again, whacking a forehand into the tramlines as he goes for the winner...

Advantage Djokovic again, and a word to the warning from the umpire that noisy fans will be sent out for disruptions between points.

The clocks ticks into hour three, and Alcaraz has another set point. Again, Djokovic is let down by the down-the-line backhand.

The Spaniard is one set from glory... and Djokovic will have to do it in five if he wants it. Goodness.

Djokovic is keen to make this hold uncomfortable, and tracks Alcaraz to 40-30 with a blistering smash that Alcaraz leaps for, like a Golden Retriever eyeing a frisbee, but can't catch.

But momentum remains with the Spaniard for now, as Djokovic recovers bent double mid-point, and he pulls off the hold when his opponent misplays his last forehand.

But this is still some contest, and against almost anyone else save for the Spaniard, Djokovic would be floating through.

Alcaraz's game is like the many-headed Hydra - just when you think you've beaten him, another marvel shot comes out of nowhere. Djokovic threw everything short of the kitchen sink at him, only for Alcaraz to find himself hitting into open court for 15-all.

Djokovic returns the favour off the next time, getting his down-the-line forehand off finally, with no attempt from Alcaraz to reply to it.

A fizzing ace tips up the Spaniard, 40-15, and the next he clouts out to the stands. The most straightforward Djokovic hold for some time.

Now it's Djokovic's drop shot which outsmarts Alcaraz, forced to sprint back in vain to make it 15-15. But just as quickly, Djokovic blunders a down-the-line forehand well out into the tramlines. Everything that worked against Sinner, he's drawing a blank with now.

A double fault should raise the spirits, making it 30-all, but a rote serve sends Djokovic deep on the forehand, only for Alcaraz to send his return into wide open court space.

He pulls off the hold cleanly. A must-win for Djokovic, coming up.

Djokovic needs a double fault like a hole in the head, but this is how he starts the fifth game, and chases it with a mistimed volley into the net high up the court. Love-30 to the Spaniard...

He thinks he's got himself level at 15-30 with a backhand down-the-line, but he misses by an inch, putting Alcaraz in the driving seat with break point.

Djokovic must get on top in this set if he has a hope... trying to pull off the win in five would be borderline deranged.

But Alcaraz takes his chance here, and immediately breaks him as Djokovic wafts another forehand out into the hinterland.

Crunch time for the Serbian.

Here's another look at Alcaraz's brief blow-up with the umpire.

During a brief technical snafu at Daily Mail Sport HQ, I can only tell you here that Djokovic held his second service game, but I'm back in action to watch Alcaraz claim a 30-15 lead in his.

Alcaraz again tilts Djokovic to sharper and sharper return angles on the baseline, and nearly sends him careening into The Norman Brookes Challenge Cup before he skews his final return into the net for 40-30.

The Spaniard is looking just as fresh in this third set, and all the more aggressive, and he takes his hold to level things up.

I almost hurled myself off my chair in excitement as cross-court exchanges ran long between Alcaraz and Djokovic, with the Serbian the winner - until Alcaraz's razor-sharp backhand proved too much for him! Stunning, stunning point.

Alcaraz has grown in stature on the baseline too, and tosses Djokovic this way and that before he hits short, bringing up 40-love.

A let, then a fault, don't get his final serve off on the best note, but he still produces something ungettable on his last chance, tipping over Djokovic to pull off the hope.

The Serbian is back on court, and there's no development in Roofgate, so it's time to get going again.

The bathroom reset hasn't taken immediately for him, as he quickly falls love-30 behind. But there's nothing like the next point to warm the blood: Djokovic is able to catch Alcaraz's audacious tweener, volley it, and watch the Spaniard fall down chasing it, 15-30.

Djokovic tracks his opponent to deuce, and gains the first advantage, pulling off the hold after Alcaraz, way back, curls his final forehand into the net.

A brief exchange with the umpire while Djokovic is off-court sees the Spaniard furiously question why the roof has been closed a little bit more.

It does look somewhat absurd, just a crack of purple sky exposed. This is an outdoor tournament, after all. It's either raining, or it isn't.

Alcaraz looks to speak to tournament director Craig Tiley, but finds another supervisor to vent his spleen to, before discussing the developments with his team.

The camera cuts to Tiley, on his phone. Which way will it move?