Hello and welcome to LIVE coverage from day two of the ATP World Tour Finals. This is the first clash from Group A - between Australian Open champion Stanislas Wawrinka and Tomas Berdych.

So Wawrinka will go top of Group A after that first match but he may only stay there for a few hours as at 8pm tonight Novak Djokovic will take on US Open champion Marin Cilic in the other Group A clash.

Wawrinka 6-1 6-1 Berdych. Game, set and match. Berdych quickly finds himself staring at two match points. But Wawrinka as he has been all match, is far too good and only needs the one, sending his reply deep onto the baseline which Berdych cannot deal with, forcing the forehand reply into the bottom of the net to end the clash.

Wawrinka 6-1 5-1 Berdych. Nothing is quite going right for Berdych today as Wawrinka gets a net cord in his favour and just waits for Berdych to do all the hard work in chasing down the ball before popping an easy forehand volley over the net for a winner that seals the game. Berdych will have to serve to stay in this match next.

Wawrinka 6-1 4-1 Berdych. Break. Another frustrated error, another break point for Wawrinka. Berdych saves it with a booming serve - the one thing that has worked well for him so far today - but Wawrinka swipes at another forehand return and sends the ball whizzing back past Berdych and into the corner across court for a winner. And this time Wawrinka does secure the double break as Berdych sends a forehand approach shot long of the baseline.

Wawrinka 6-1 3-1 Berdych. Another very quick and easy service hold for Wawrinka to consolidate the early break in this second set. Unless Berdych can come up with something special quickly, Wawrinka looks to have this match won.

Wawrinka 6-1 2-1 Berdych. Break. Berdych is left shaking his head in frustration as he once again is forced into the error - a backhand long - by Wawrinka, gifting the Swiss player just another break point in the process. Berdych manages to save it with a big first serve but is denied on a game point of his own when Wawrinka pulls him around every point on the baseline before stretching out to dink a forehand stop volley winner just over the net. Ultimately, though, Wawrinka is too relentless for Berdych as he wears the Czech down and breaks with a booming forehand that Berdych cannot return.

Wawrinka 6-1 1-1 Berdych. Wawrinka, clearly keen to dispel any suggestion to Berdych that he is gaining any kind of foothold in this match, races through another quick and easy service hold to keep the pressure on his Czech opponent.

Wawrinka 6-1 0-1 Berdych. Much, much better from Berdych as he enjoys his easiest service game of the match so far. An ace seals the hold in much more confident fashion than we have seen from the Czech so far today and that was an important, morale-boosting hold for him.

Wawrinka 6-1 Berdych. Set. Another very emphatic service hold from Wawrinka to close out the set, despite a challenge on the last point. Just 24 minutes that set took, not unlike Wawrinka's compatriot Federer against Raonic last night.

Wawrinka 5-1 Berdych. Berdych earns himself a game point when Wawrinka completely mis-times a forehand and hits the ball far higher into the air than he can manage to get it forwards to the net. But the Swiss player more than makes up for it on the next point, swishing a forehand return over the net across court for a winner and then quickly becomes a set point for the Aussie Open champion. Berdych saves it with an ace before going on to hold and get himself belatedly off the mark. Wawrinka will serve for the set after next.

Wawrinka 5-0 Berdych. This is fast turning into a rout for Berdych as Wawrinka eases through another service hold, the Czech player netting a forehand on the final point. Berdych will have to serve to stay in this opening set after the change of ends.

Wawrinka 4-0 Berdych. Break. Ouch. Three quick errors in succession and Berdych finds himself staring at another three break points. Wawrinka only needs the one though as he puts his dipping return low over the net and draws a backhand volley error from a crouched Berdych.

Wawrinka 3-0 Berdych. A comfortable hold to 15 for Wawrinka to consolidate the early break. The only blip in the game from the Swiss player came when he mis-hit a routine forehand and put the ball long. Wawrinka looks very at ease in this game so far as he looks for a continuation of his recent domination over Berdych.

Wawrinka 2-0 Berdych. Break. Wawrinka puts some early pressure on Berdych as he slices a single-handed backhand down low to the Czech player, drawing the error, to level at 30-all and then also at deuce with a forehand winner across court. That then quickly becomes the first break point of the match when Berdych loops a forehand long, replying to a very good forehand return from Wawrinka. And sure enough the Australian Open champion does grab the early break when Berdych again sends a forehand long.

Wawrinka 1-0 Berdych. Some big serving from Wawrinka to get the clash underway as he holds to love when Berdych's inside out forehand catches the top of the tape and fails to go over.

The players are just about ready to go and it will be Wawrinka to get the clash underway, after winning the toss and opting to serve first...

In fact, Wawrinka has won seven of their last eight clashes - albeit being pushed to three tie-break sets out of four in that meeting at the Australian Open in January.

These two have faced each other 14 times before with Wawrinka leading the head-to-heads by nine wins to five, including victories at this stage of the ATP World Tour FInals last year and in the Australian Open semi-finals at the beginning of the year - their most recent meeting.

Later on today is the second of Group A's clashes - between world number one Novak Djokovic and US Open champion Marin Cilic.But for now it's Wawrinka and Berdych about to take to the court.