Just as in the first set, Konta gives up a break with a double fault. Petra Kvitova will serve for the match.

There's some chat that both Konta and Kvitova currently have a faster second serve than Andy Murray. Unconfirmed, but good enough for us to print. In the New York night, Konta just begins to squander a 40-0 advantage as Kvitova finds her length. 40-0 to deuce. Oooohhh, and a loop long from Konta give Kvitova break point...

Slight delay at the start of this 10th game as Murray waits for the Armstrong crowd to take their seats after a Mexican Wave...

Anderson's career has not been built on his prowess at the net, but the big-serving South African is proving he is not a one trick pony. He moves into the net twice during the ninth game of the fourth set, helping him to hold without any reply from Murray's side of the net. Now Anderson is one break of serve away from his first Grand Slam quarter-final....

Christophe Talbotski: Andy Murray US Open 5 set epics. Making night shifts bearable since last week

Kvitova, heavy strapping on her right thigh, is looking rock solid. A rapid hold to love. The crowd on Ashe is swelling, coming in to for An Evening With Roger Federer. The pre-show isn't bad at the moment, Johanna Konta moving herself up the tennis bill.

We're rattling through the service games now on Louis Armstrong Stadium. Murray blasts his way through Anderson's defence, finishing him off with another ace. Now can he find a chink in the South African's armour?

Anything Murray can do, Anderson can do equally as well. The South African loses the opening point to give Murray a ray of hope, only to strangle the life of the Briton with his thunderous service game. Ace! Ace! Ace! Three more quality serves nudge Anderson back ahead.

Image source, AFP

Jonny Guy: Worth missing out on sleep for this, what a match. Murray is in real danger though, come on Andy!

Kenny Simpson: Andy shouldn't be putting us all, especially Kim, under this much stress!

Konta's slight issue is that Kvitova's earlier serving wobbles seem to have dissipated. No sign now that the fifth seed might might let the Briton in. That means Konta must keep holding, which she has done all night, bar for one lapse at the end of the first set. At the far end, she is forced to scamper, eventually being out-run for 30-30. With her brown hair tied in a ponytail, Konta holds on when Kvitova sends a return long. It's a slugfest.

Just what Andy Murray needed - a hold of serve that doesn't expend too much energy. The Briton smashes down his 15th ace of the match to wrap up the game.

Jeff Tarango
Former professional tennis player on BBC Radio 5 live sports extra

"Anderson barely made it to his chair there. He was like a boxer who has taken some big hits, not knowing where to sit down. He's able to serve - he'll be able to do that until he's 95 years old, but the lateral movement is a problem."

Any hope/fear* that Kevin Anderson might run out of steam is not materialising at the moment. A minor wobble gives Murray hope at 30-30, but the South African rediscovers his quality with a backhand volley winner at the net to keep his nose in front.

* delete as appropriate

Konta turns her racquet in her hand every time she bounces the ball, a very deliberate action. She's the hunted in this second set, playing catch-up, knowing a mistake could end her golden run. Mistake, though, aren't really in the make-up of the new and improved Johanna Konta. A hold to 15.

Jeff Tarango
Former professional tennis player on BBC Radio 5 live sports extra

"I was listening to that, but I couldn't watch. I was just too nervous. Andy is getting smarter, Anderson is getting a little more desperate. He'll still be able to serve, though."

Andy Murray quickly wipes his furrowed brow after saving another break point. A forehand winner puts within touching distance of an important hold, which the Briton clinches by unleashing a monster of a first serve.

Image source, Getty Images

Oh my word. A ridiculous forehand from Murray, who was slipping and stretching before somehow recovering a penetrative Anderson forehand, gives him a game point. But he just can't shake off this pesky South African. Another chance for Murray to close this one out goes begging before Anderson sets ups a second break point of the game....

While the crowds roar on Armstrong, there's the merest ripple of applause on Ashe. Konta looks in a spot of bother at 0-30, but finds the angles to drag it back to 30-30. Her serve is looking a little wobbly, mind, and she has to battle to a lengthy hold. She still looks ice cool, though.

Max Sopel: Konta should have won first set, Murray should have broken. I should be in bed.

A bullet of a forehand from the baseline flies past Murray and into the blue screen behind the Briton as Anderson goes 30-15 ahead. But Murray hauls himself level before going long with a backhand. Break point Anderson....

Murray dupes him with an undercooked first serve, Anderson pouncing too early and going long. Deuce....