Juan Martin del Potro lays down his own law with a commanding service hold.

After than one sloppy service game from Andy Murray, it is looking tricky for Great Britain to bust back into this set.

Great Britain are on the board, but not without a little smidge of controversy.

Jamie Murray, eager as a beaver, flicks away a volley to win the final point from almost on top of the net.

Actually was he literally on top of the net?

Juan Martin del Potro asks the question of Pascal Maria, playfully tugging the umpire's tie to emphasise his point.

Pascal Maria says no. It was close.

Happier times.

Watch Andy and Jamie Murray wrap up the opening set is super-swift style.

Image source, Reuters

One of the oddities of the Davis Cup is that instead of each team being decked out in matching playing outfits - like they are at the Olympics -  each player's personal kit sponsor puts together a version of the national colours.

Which means that Juan Martin del Potro and Leonardo Mayer look like they have has a rummage in lost property for their playing shirts and come up with the closest two shades of blue that they could.

They are looking the part on the scoreboard though. They are three to the good with the break.

Andy Murray's serve has suddenly gone walkies.

Two double-faults in three points give Argentina a free pass to deuce and then offers up a break point to the visitors.

Uh-oh, the touch at the net is also AWOL.

Andy Murray duffs a half-volley pick-up wide of the mark and Argentina, after being battered in the first set, are ahead in the second.

Harleen Quinzel: Can we fire the Argentinian captain? What was he thinking? Horrendous decision. Lost themselves the tie. 

KGR: Murray brothers have come out strong! Jamie is on fire.  

Gary Jeffrey: This is more like it! #BackTheBrits

Juan Martin del Potro's serve is a mighty beast of a stroke - a grass-reared, free-range monster.

A hold to love. The Murray brothers may well decided that the Leonardo Mayer service games are the ones where they can pick up some points against the head.

Image source, AP

Jamie Baker
Former GB Davis Cup player on BBC One

The GB bench are absolutely rejuvenated - compared to the singles last night with Kyle Edmund there is not a space out here. I think Leon Smith and the rest of the team have had a talk and said ‘Come on, let’s raise our energy.’

Jamie Murray's razor-sharp reflex volleys and Andy Murray's bullish serve turn a little bit of a sticky situation at 15-30 down round to 40-30.

Another serve bristling with intent and that is the first set cooked.

Twenty six minutes on the clock.

Proclaimers on the stereo.

Jamie Murray's lob return - the Scot's favoured shot on the doubles circuit - puts Argentina back on the baseline and set up a two pronged Brit attack on the net.

It's a cunning tactic. One point earned off it, but Argentina are belatedly on the board.

Andy Murray to serve for the first set next.

John Lloyd
Former GB Davis Cup captain on BBC One

There is no doubt Del Potro would have been the one who decided he would play today but I can't see how logically they would think they’d win this doubles. So why would you tire him out? Although if it carries on like this, it’s like a warm-up – no harm done!

Seventeen minutes gone, five games gone and they are all posted up on the Great Britain side of the scoreboard.

Andy and Jamie Murray are making mincemeat of the prime Argentine cuts on the other side of the net. 

Image source, Getty Images

So far, this Argentine experiment of shoving Juan Martin del Potro back on the front line to try and bring the tie to an early conclusion is not going well.

The Murray brothers - and Jamie especially - have come out of the blocks firing.

Leonardo Mayer less so.

Another strange smash from the junior partner in the Argentine partnership helps set up a first break point Britain.

The Del Potro serve saves that one, but Andy Murray makes a second one stick as he flogs a return across court, into the doubles alley and away for a clean winner.

Image source, Getty Images

Jamie Murray is crawling all over the net like slugs in a lettuce patch.

The older brother puts away a couple of volleys at such tight deadly angles that the umpire is in more danger of being smacked than the Argentines.

He looks like he is determined to take the lead and give Andy a free ride into his second singles rubber.

Great Britain break to love and the girders of the Emirates are creaking once again.

Leonardo Mayer's serve is an all-you-can eat buffet for the Murray boys and they chow down.

The game is sealed when Mayer inexplicably clouts a gimme of an overhead smash out on the full.

Image source, Getty Images

Miles Maclagan
Former British Davis Cup player on Radio 5 live sports extra

After yesterday’s match the recovery would have involved ice baths, massage, maybe a bit of acupuncture. It’s a bit of a surprise to see Del Potro out there again today but he’s already had a couple of telling moments.

Leonardo Mayer muffs a couple of makeable volleys at 15-15 and is almost punished corporeally as Jamie Murray whacks a winner past his cowering midriff.

Andy Murray needs to get his eye in at the net, as he allows a dipping shot to whizz past his waiting racquet.

No matter.

Great Britain are home and hosed and the Stirling University Barmy Army is in full well-lubricated cry.

Image source, Getty Images

Jiten Chandarana: Jamie's forehand block return may be key. JMDP likes to go big up the 'T' on the deuce and out wide on the ad.

Daniel Potter: Decent of Andy to play today he must be knackered!

Ben Silveston: Credit to Andy Murray for playing again after the marathon match yesterday! Let's hope he and Jamie can win!  

Jamie Murray will tee us off.