Welcome to LIVE text coverage of Tomas Berdych's must-win World Tour Finals clash with Janko Tipsarevic at the O2 Arena in London.

BERDYCH 2-6 6-3 7-6 (8-6) - GAME, SET AND MATCH! Berdych edges out Tipsarevic in a hugely dramatic and emotional final set tie-break, and what a match it was! Tipsarevic limps away looking very rueful after taking a tumble striving for a forehand in the final point, and hopefully he is okay. Berdych secures his first victory of the tournament! Thanks for joining us.

BERDYCH 2-6 6-3 6-6 (5-5) - Berdych assumes control at 5-3, but two unforced errors ensure that Tipsarevic is able to level the breaker up at 5-5 - what drama!

BERDYCH 2-6 6-3 6-6 (3-3) - There's nothing to choose between the pair as Berdych volleys superbly cross court to deny Tipsarevic after the Serb had forced the early running.

BERDYCH 2-6 6-3 6-6 - We're into a final set tie-break! Tipsarevic gives it his all as he attempts to break serve at the death and force victory, but Berdych holds firm and shows incredible resilience to hold serve and take this final set into a breaker!

BERDYCH 2-6 6-3 5-6 - Berdych is unable to force his way into the game as Tipsarevic fires three first serves outwide to keep the Czech stretching out of court, and he closes out another crucial service game to thwart his opponent.

BERDYCH 2-6 6-3 5-5 - Tipsarevic again forces Berdych out to 30-30, but the Czech responds with two enormous first serves to force his opponent back on the court and hold to level at 5-5. It's getting extremely cagey now!

BERDYCH 2-6 6-3 4-5 - Tipsarevic is relishing this stage as the match remains very finely poised, and he holds serve with a crushing forehand down the line sealing the game as the onus switches to Berdych to hold serve under real pressure.

BERDYCH 2-6 6-3 4-4 - Berdych is forced out to deuce in a hugely competitive game, but the Czech holds his composure with a fierce forehand winner following a big first serve to take the game under pressure and ensure that he levels at 4-4.

BERDYCH 2-6 6-3 3-4 - Tipsarevic again shows his class and guile as he moves Berdych around the court like a puppet and shows incredible touch as he pulls off a superb drop shot! Tipsarevic can now apply real pressure of his own...

BERDYCH 2-6 6-3 3-3 - It's nip and tuck as Berdych hammers a forehand down the line, and he relies upon that wing to produce for him again as Tipsarevic forces his opponent back on the court, but he responds with a string of powerful blows.

BERDYCH 2-6 6-3 2-3 - Berdych does his utmost to apply the pressure on his opponent on return, but Tipsarevic keeps his cool and finds three precise first serves to hold serve and keep his nose in front in this third and deciding set.

BERDYCH 2-6 6-3 2-2 - Berdych's serve has been transformed since the opening set, and the Czech bludgeons a forehand cross court to close out the game in emphatic fashion! Tipsarevic must again hold under pressure now.

BERDYCH 2-6 6-3 1-2 - Tipsarevic again holds his composure with a solid hold, and Berdych is unable to halt his opponent's progress. Tipsarevic will now look to pile the pressure on his opponent's serve...

BERDYCH 2-6 6-3 1-1 - Berdych has no problems in levelling at 1-1 as he finds a string of fierce groundstrokes, and the Czech is thriving now as he looks to continue his momentum in this deciding set.

BERDYCH 2-6 6-3 0-1 - Tipsarevic holds serve stubbornly with real determination as the Serb establishes himself at the start of the third set in confident and assured fashion. He clenches his fist in delight as he takes it!

Who are you backing to win this deciding third set? The momentum is with Berdych now, but can Tipsarevic raise his game once more?

BERDYCH 2-6 6-3 - SET! Berdych is serving much better now, and the Czech fires three enormous first serves to keep Tipsarevic pegged firmly back behind the baseline before slamming a forehand cross court to hold serve and take the second set!

BERDYCH 2-6 5-3 - BREAK! Berdych takes control of the second set with an inspired game! Tipsarevic wavers slightly and loses his rhythm on serve, and Berdych ruthlessly capitalises to move to within a service hold of taking the second set and levelling up this match!

BERDYCH 2-6 4-3 - Berdych keeps his nose in front in this second set as he fires a string of huge forehands to dent Tipsarevic's resistance and to close out the game. This second set is very finely poised...

BERDYCH 2-6 3-3 - Tipsarevic again levels up pretty nervelessly, and the Serb is showing no signs at all of erring in this second set as Berdych looks to pile on the pressure, but to no avail at the moment.