Good evening and welcome to LIVE game-by-game coverage of the ATP World Tour Finals Group B showdown between Roger Federer and Andy Murray. The players are due on court just after 8pm GMT.

GAME, SET AND MATCH! - FEDERER 6-0 6-1 MURRAY - The Swiss Maestro destroys Murray inside an hour, dropping just one game along the way. It's a real low point in the career of the Scot who bows out of the tournament with barely a whimper. Fed-Ex marches on and tops the group meaning he will most probably avoid a semi-final clash with Novak Djokovic.

FEDERER 6-0 5-1 MURRAY - Finally! Murray gets on the board and the fans respond with a loud roar of approval. They don't want to go home yet, but you sense it merely delays the inevitable by a few moments. Initially, a sublime Fed-Ex drop shot followed by a double fault has the Scot's shoulders slumping further. Murray manages to claw a point back and then somehow conjures up a second serve ace to level. Federer blows a forehand long and then can't return a big first serve as Muzza breathes a big sigh of relief.

FEDERER 6-0 5-0 MURRAY - It's all too easy and over in the blink of an eye. It's exhibition stuff from Federer as Murray toils. The Swiss is in no mood to take pity and holds to 15 to move within one game of the double bagel.

BREAK! - FEDERER 6-0 4-0 MURRAY - Murray contributes to some outstanding rallies and twice gets himself in to winning positions - only to allow the Swiss back in. A 19th unforced error into the net hands Federer another break point and the Scot drills his next shot long to drop a 10th straight game. It's a desperate evening for the British number one who could be on for night that will be right up there as a career low.

FEDERER 6-0 3-0 MURRAY - Even when Murray finds a glimmer of hope, Federer ups his level and dismisses him with nonchalant class. The Scot digs in at 15-30 but has no answer to the Swiss Maestro's range of sublime strokes as he roars back to consolidate the break. It's looking like an early dash home for all of those fans in the O2. They would have anticipated more of a contest than this!

BREAK! - FEDERER 6-0 2-0 MURRAY - This is becoming HUGELY embarrassing for Murray. It's an absolute annihilation so far. The Scot edges into a 30-15 lead with a nervy volley at the net but faces another break point when a sublime dropshot from Federer is followed by a double fault. The Brit's tame second serve is then brutally returned with extras and Muzza can only block it long to lose an eighth game in a row.

FEDERER 6-0 1-0 MURRAY - Fantastic Federer continues to maul Murray with terrific tennis. It's a hold to 15 as Muzza nicks only his ninth point of the match so far!

SET! - FEDERER 6-0 MURRAY - It's a bagel and the end of the line for Murray. He's playing for pride now. The Scot's error-strewn display continues as a magnificent Federer breaks again to seal it in double-quick time. Nishikori will play in the last four.

FEDERER 5-0 MURRAY - Nevermind, winning in straight sets, Murray is looking at damage limitation here. A bagel is on the cards for the Swiss who has completely outclassed the Brit. It's another game to love and this contest is passing him by all too quickly.

BREAK! - FEDERER 4-0 MURRAY - Federer has got his mojo working and Murray looks out of his depth. The Swiss sears a shoulder-height forehand down the line and follows it up with a devastating smash at the net. Muzza can't keep pace with him and drives way, way long to drop another service game to love.

FEDERER 3-0 MURRAY - Roger consolidates the break with an emphatic love hold. Remember, Murray can't afford to drop a set here but he's already up against it. He couldn't have dreamed up a worse start and it will be hugely impressive if he recovers to go through from here.

BREAK! - FEDERER 2-0 MURRAY - It's a disaster for the British number one as he drops a rollercoaster game after saving one break point. In truth it was a game of errors from both players with the pick of the action coming at 15-15 when the Swiss Maestro lay the foundations for the break with a delicious drop shot followed by a delicate lob that bamboozled his opponent.

FEDERER 1-0 MURRAY - A big chance for Murray goes begging right at the start. The Scot works a 0-30 lead but then sees a net cord go against him following an epic 35-shot rally. The Swiss benefits from another ripple off the net and goes on to seal the hold. An intriguing start but it could be one Murray looks back on as a missed opportunity tinged with a slither of misfortune.

Here we go: Federer to serve first...

Not many of you can see Murray winning here, but @Tennis17MAD offers some thoughts on what the Scot will need to do to pull off the shock success. He says: "Murray has to go all-out tonight. Compete at his attacking-best. The only way he will win in straights."

A comedy coin toss needs a second attempt with Fed-Ex winning it and electing to serve first. Time for the warm up and then it's showtime!

On Twitter, @Dozie1644 reckons Murray will come up short. He says: "Going to be a tough call for Andy tonight. I don't see him beating Federer in straight sets."

THE BLUEPRINT FOR MURRAY: The Scot blitzed Federer to win Olympic gold back at London 2012. A repeat of that performance would surely be enough to send Muzza through... but Federer remains favourite to win the match and make it three wins from three in this pool.

This is a huge match for Murray. A win would be a great achievement, but that isn't enough for the Scot. He needs to triumph in straight sets to make the semis. Can he do it? Federer is already there but will be keen to avoid a last four showdown with Novak Djokovic, who is red-hot favourite to top Group A. Tweet @paul_hassall your views and I'll include your comments in-between games.

Federer is well aware of the dramatic improvement that saw the Scot book his place at this tournament and is expecting a fired up Murray come out all guns blazing. He said: "I'm sure his belief is higher now again. Beating David Ferrer twice, and Marin Cilic as well in Beijing, Jo-Wilfried Tsonga at the US Open - those are the matches he needed to win down the stretch at the end of the season, which he did."