Hello and welcome to LIVE updates from Day One of the Davis Cup semi final between holders, Great Britain and Argentina at Glasgow's Commonwealth Arena. First up, it's the big one. World number two, Andy Murray against Juan Martin Del Potro. The players met as recently as the 2016 Olympic final where the Scot came through a gruelling four-hour+ war of attrition to claim a second successive gold medal. It promises to be a key battle in the tie and all gets underway from 1pm BST.

Highlights: Juan Martin del Potro sinks Andy Murray

GAME, SET AND MATCH! - MURRAY 4-6 7-5 7-6 3-6 4-6 DEL POTRO. An extraordinary battle comes to a close after five hours and seven minutes as Del Potro lands an ace to serve it out to 15. Argentina move 1-0 ahead in this semi final tie as Delpo gets some small measure of revenge for the Olympic gold medal match Murray won in Rio. It's a contest befitting an occasion of this magnitude as Juan Martin goes toe-to-toe with GB's talisman, Murray and comes out on top with some powerhouse tennis. It's tough to take for Muzza who has had to contend with a family bereavement this week and he gave everything on court in what proved to be the longest match of his career. The holders face an uphill battle from here.

Five hours and three minutes... Quite simply epic!

MURRAY 4-6 7-5 7-6 3-6 4-5 DEL POTRO. Incredible serving from Murray. He lands five aces on his way to a hold from deuce, saving a match point on the way. Big cheers from the crowd but the key moment is up next. Del Potro to serve for the match.

MURRAY 4-6 7-5 7-6 3-6 3-5 DEL POTRO. JM consolidates to 30 despite some positive play at the net from Murray. The Scot must now hold to stay in the match.

Ha ha, brilliant.

BREAK! - MURRAY 4-6 7-5 7-6 3-6 3-4 DEL POTRO. A clench of the fist from Del Potro. Has he secured the all-important break to go on and win this match? The Argentine roars to triple break point. Murray hits back with brave tennis to save two and thinks he's reached deuce, but he reckons without the brilliance of Delpo who sizzles a pass down the line on the run to move in front in this decider. Are Argentina on the verge of a 1-0 lead in this semi-final tie?

MURRAY 4-6 7-5 7-6 3-6 3-3 DEL POTRO. JM's ranking of 64 in the world is simply because of the injuries he's endured. A top six player no question when he's fit and firing. Murray puts him under the cosh with a crosscourt winner on the run the most eye-catching of the points as they battle away to deuce. The Brit pushes for a break opportunity but the Argentine closes the door. We are level once more as the set edges towards the business end.... No room for a slip now...

MURRAY 4-6 7-5 7-6 3-6 3-2 DEL POTRO. A huge hold for Murray. The Brit saunters 40-0 up but then contrives to lose the next four points and offer up the first BP of the set. He saves it with a beast of a serve down the middle T before outlasting Delpo in a fierce rally and then guiding a crosscourt volley into the empty space.

MURRAY 4-6 7-5 7-6 3-6 2-2 DEL POTRO. What a gruelling game. Del Potro is pushed to a few groundhog days at deuce after leading 40-15. Murray's defence and resilience is commendable but Delpo is equally gritty. That's why we are into fifth hour here. All square.

MURRAY 4-6 7-5 7-6 3-6 2-1 DEL POTRO. Murray nicks the line to finish with an ace as he cruises through a hold for the loss of one point. Both players solid on serve so far... the calm before the storm?

MURRAY 4-6 7-5 7-6 3-6 1-1 DEL POTRO. JM brushes off a mini Murray revival from 40-0 down to hold to 30. All square. Tight...

MURRAY 4-6 7-5 7-6 3-6 1-0 DEL POTRO. Murray gets off to the perfect start with a love hold. He has the scoreboard advantage. An early break anyone?