Andy Murray v Roger Federer, ATP World Tour Finals semi-final: live 20.24 Murray* 4-2 Federer Murray struggling to get his first serves in and it lets the door open for Federer. I speak too soon as Murray recovers with a timely booming first serve and follows it up with a 136mph ace as the game moves to deuce. Murray dispatches a backhand smash at the net with Federer sniffing a break point chance but Murray advances to the net again to restore his two-game cushion. 20.19 Murray 3-2 Federer* Murray has the edge of the early baseline rallies with some deep-hitting groundstrokes really leaving Federer's footwork in a muddle. Another mini-break opening for the Scot lifts the crowd but Federer doesn't make a mistake with another volley to prevent a break-point shot. Federer starts to find his groove and sees out the game. 20.15 Murray* 3-1 Federer Federer's unforced errors already creeping up at a vast rate (seven and counting). A lucky net cord lands favourly for Federer but not so as he smashes his volley into the net for 40-15. Murray hits a wild forehand but responds with a strong first serve. Jason Mak on who should play Murray on the big screen: I think Andrew Garfield (the leading actor in the latest Spiderman film) would be a good choice - he looks just like Murray in my opinion! 20.10 Murray 2-1 Federer* Murray injects a bit of pace into his backhand return and catches Federer flatfooted. The Swiss maintains his composure to move to 40-30 with some neat serve-volleying but Murray reels him in. Murray swipes at a return which almost lands inside the line and a 'oooh' goes up in the crowd. He can't make another return and Federer registers his first game. 20.06 Murray* 2-0 Federer Both players decked out in dark outfits, Federer almost camouflaged against the blue surface, but it's a bright start by Murray, hitting a sweet sliced backhand inside the line to win his first point off his serve and manages to keep Federer on the backfoot. Wraps up game when Federer hits into tramlines. 20.01 Murray 1-0 Federer* Quick start by Murray taking opening two points by jumping on a Federer second serve and going a mini-break up. Federer responds with an ace but Murray has first sight of two break points when he outlasts the Swiss in a long rally. He can't take the first one but an unforced error from Federer sees him edge in front. 19.50 Murray wins the toss and opts to receive. Queue warm-ups. 19.49 Murray strolls through the dry ice and a roar goes up inside the O2. Federer follows and is matched by the same wall of noise. Home advantage it may be for Murray but Federer has at least half the crowd on his side. 19.45 Murray was a player who used to get under the skin of Federer, but maybe the Swiss has mellowed in his old age. Or perhaps he's adopting some good old-fashioned mind games by championing his opponent ahead of tonight's match. Federer said of Murray's Olympic triumph after losing Wimbledon final: "I always hoped he would have a reaction like this, to be quite honest, even though it cost me maybe a gold medal. I think his drive was so strong, at the end, that it carried him through. That's the sign of a champion. Now he's up there and he will be for a very long time. Think back four years ago when Federer was quick to knock down Murray's passive style of play. Then he said: "I don't think he has changed his game a whole lot since the first time I played him and I really thought he would have done." 19.30 Disappointment for one Brit already this evening as Jonathan Marry and doubles partner Frederik Nielsen have lost their semi-final contest in straight sets to Marcel Granollers and Marc Lopez. Hope it's not a sign of things to come. 19.20 Good evening and welcome to coverage of the second semi-final from the O2 where Novak Djokovic waits to find out who he will face in Monday's final having recovered from a set down to beat Juan Martin del Potro earlier in the day. Locked at two wins apiece from their four duels already this season, Andy Murray's semi-final clash with Roger Federer holds more than just bragging rights for who will edge their head-to-head record this year. Both players are striving for their third final on British soil in the last four months after sharing one title each, Murray recovering from 'that' Wimbledon final defeat to beat Federer just three weeks later and clinching the Olympic gold medal on the same hallowed SW19 turf. This has the makings of another blockbuster between the two-time defending champion here in London and the US Open champion, which makes me ponder. If a film were to be made of Murray's success this summer, who would play the young Scot? Murray should be fresher having had an extra day to prepare for tonight's semi-final with Federer losing his final round-robin clash with Del Potro yesterday afternoon (albeit having already qualified for the last four).