Andy Murray rouses himself and tunnels back to the relative safety of deuce with a clouting ace.

Deuce.

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The wheels have got very wonky all of a sudden on the Murray wagon.

A double fault offers Juan Martin del Potro three break points.

John Lloyd
Former GB Davis Cup captain on BBC Two

That call really affected Murray there. Very rarely does he miss two returns in a row.

This match is starting to get frayed and fractious.

Juan Martin del Potro inexplicably pattercakes a volley straight back at Andy Murray when he should be blasting an overhead through the backboards.

That gives the Scot 15-30.

But what the Argentine giveth, the myopic line judge taketh away.

A Murray forehand is called out, Murray appeals and the video replay shows it was well in.

"A disgusting call," is Murray's verdict. The Scot is wobbled by it though and loses the next three points.

Andy Murray lashes down his service game to love.

John Bercow - speaker of the House - is in the crowd by the way. 

He is wearing a Back the Brits t-shirt over the top of some sort of collared number.

Not quite Williams Hague's baseball cap, but more evidence that politicians stuggle with civvies.

A minor missed chance, but a missed chance nonetheless.

Andy Murray is into the net and in charge in the rally at 40-30.

His forehand volley though floats tamely to the baseline, neither punched away for a winner or pushing Juan Martin del Potro out into the wing.

Del Potro summons up a punishing pass.

It was not a big chance, but it was a chance. And Murray needs to take his today.

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John Lloyd
Former GB Davis Cup captain on BBC Two

That was a very good hold from Murray. Del Potro came back at him a little bit but Murray got his act together.

It looks like Del Potro has got rid of all the anger at losing that second set with the interference from the crowd.

He has regained his composure, he's back to business.

After another battle from the back of the court, Murray prevails to break the Del Potro serve. Press play below to watch the world number two take the second set.

Right then, best of three? Let's.

Andy Murray is on the rack in the opening game of the third set.

Thirty-all and it looks like he has just missed his target down the line.

Murray appeals to the gods of video and Hawkeye delivers showing he smudged the line.

Replay the point.

Murray comes bustling into the net and swipes away a drive volley. A rooster-booster of a serve and he is home and hosed.

A big play from the IT crowd in that game.

Point of the match so far comes from Andy Murray. He somehow not only manages to race back to retrieve Juan Martin del Potro's lob, but then turns it into an outright winner with a fizzing forehand down the line. 

Great Britain's Dan Evans, speaking courtside to BBC's Jamie Baker: "Andy had to get that set. It is still in the balance, I still back Andy but it is going to be another two or three brutal sets.

"It tough to keep going to Del Potro's backhand because there is no pace but if Andy does go to the forehand you get burnt cross court.

"I wouldn't like to be sat on the bench telling Andy what to do in that position."

The Argentina camp are more than a little miffed about the crowd noise that was going on during the final point of that second set.

There is a lot of gesticulating around the base of umpire Pascal Maria's chair.

Think Antonio Rattin in 1966 and then tone it down a few notches,

But distinctly disgruntled.

A rally with both players pushing groundstrokes right up to the whitewash.

The Stirling University Barmy Army think that Juan Martin del Potro has strayed long.

They make a load of noise. The line judge stays silent though.

On goes the rally amid equally loud hushes.

That one is definitely long from the Argentine though!

Parity!

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Juan Martin del Potro blots his forehand copybook, cuffing an open invitation of a mid-court bounce wide to hand Andy Murray a sniff at 15-30.

More than a sniff. A really good snort of a chance.

Murray with a forceful forehand, into the net and he slaps down a volley for two break points!

John Lloyd
Former GB Davis Cup captain on BBC Two

You have to give Murray credit for that serve.

This match is really outstanding, the quality to magnificent.

Del Potro did nothing wrong in that game but Murray elevated this game when he had to.

Andy Murray's 13th ace comes at a fortunate time, knocking Juan Martin del Potro back from 15-30 up.

His 14th follows straight after.

And a deft forehand volley on the cutest of angles means Murray is into a tie-break at the very least.

Image source, Getty Images

John Inverdale
BBC commentator in Glasgow

With that one shot Murray has lit the touch paper in this arena.

John Lloyd
Former GB Davis Cup captain on BBC Two

We are coming to the end of the season, when Del Potro can work on strengthening that wrist. 

He is going to be a major threat next year.

Wowzers.

Andy Murray chases back to his baseline in pursuit of a Juan Martin del Potro lob.

The Argentine has a prime position on the net. Murray is spinning and hitting blind. No matter.

A brilliant blast down the line is just too good. Del Potro gets a flick of frame to the ball but no more. 

15-30, Murray two points away from the second set and parity.

But Juan Martin del Potro is pressure-proof. Plunge him to the bottom of the Marianas Trench and he wouldn't flicker.

He wins the next three points - aided by a bit of a rogue shout from the crowd on one - to see off the danger.

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