One hour and 23 minutes and the set has gone Andy Murray's way!

Del Potro can barely believe it as he sends a return down the line and it bounces out! He gets the umpire out of his chair to check, but he confirms it's out. Del Potro stands at the net for an age, staring at the court. He had four set point chances. How big a miss will that be?

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Lovely. Del Potro doesn't return Murray's serve well and Murray has plenty of time to tap over another drop shot. Now it's Murray's third set point...

Del Potro hits the net! Oh this is just brilliantly daft, the rally going this way and that before Del Potro floats his backhand into the net.

Oh! Magnificent from Del Potro! Murray was on top and then just the tiniest of forehand dabs over the net and the ball landed perfectly. Set point four!

Double fault! How?! Del Potro smashes his racquet into his head in annoyance!

Thought Kevin Anderson would go away quietly? Don't be daft.

More aggressive tennis from the former world number 10 sees him gain an early advantage in the fourth set.

A routine hold to love is followed by a peach of a returning game which yields three break points. He needs just one. That's eight points on the bounce for the South African.

Then we hear a massive roar from over on nearby Chatrier. Is there something exciting going on over there?!

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Oh! A bobble off the net falls awkwardly for Murray, he returns it and Del Potro, somehow, sprawling to his right, picks up and slaps the ball beyond Murray! What a set...

Long! Murray's sent his forehand over the baseline! Dearie me.

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Ah. That's a wonderful bit of serving from Del Potro, down the line, and he saves the first set point. Back to Murray...

Feet scuffling around all over the show and Murray gets the upper hand with another one of those drop shots! Two set points to Murray...

Another serve volley from Murray and Del Potro sprawls yet again. Pressure back on Del Potro...

And we're back to parity straight away as Murray throws everything into his serve, then follows it up with a wave of his racquet at the Spidercam.

Into the net from Murray! He's dragged himself into that rally but Del Potro's forehand just kept coming.

Simon Briggs
Daily Telegraph tennis correspondent on BBC Radio 5 live

You can't blame either of them for feeling anxious. The prospect of going behind early with the history there is between them is too painful to contemplate.

Wide on the forehand from Murray, and he's not happy with himself. He's not been too verbal today but he mutters into the towel as he wipes his face.

That's a corker of a second serve from Murray and he's in control of this rally all the way. 21 shots, and eventually Del Potro spoons his response high and long. Another long return from the Argentine, and now we're on serve...

A backhand goes awry from Murray, only finding the foot of the net, but now it's Del Potro who skews his return wide! Does no-one want to end this?!

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Murray double faults for the first time this match! What a time to do it. That's a mini-break to Del Potro...

One more hold will do it. You've managed 17 already Kyle so another shouldn't be too hard, should it?

No!

The Briton starts with an ace as he gallops 30-0 ahead, a ropey backhand giving Anderson a glimmer, but a set point appearing when the South African batters a forehand over the baseline.

And he seals the third set when Anderson misses the target again. The British number two is one set away from the fourth round...

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A wry grin and a shake of the head from Murray as Del Potro plays him at his own game with a dinky backhand drop shot.

The Argentine's serve isn't as effective as it was at the start of the set but that's another magnificent drop shot and Del Potro will hold. We're into a tie-break!