Novak Djokovic added another processional victory to the lengthening list at the ATP World Tour Finals with a 6-2, 6-2 demolition of subdued Czech Tomas Berdych on Friday.

The world number one was virtually guaranteed a semi-final berth before walking on court at the O2 Arena, but made doubly sure by cruising past Berdych in little more than an hour.

A day after Roger Federer dropped only one game beating home favourite Andy Murray to win Group B, Djokovic was also in ruthless mood to top Group A and guarantee ending the year ranked as world number one for the third time.

The Serb has now won 30 indoor matches in succession since the ATP World Tour Finals in 2012.

Of the 11 round-robin matches played at the tournament this year only one has gone to a deciding set.

Djokovic, looking for a third consecutive title at the London year-ender, will face Japan's Kei Nishikori in the semi-finals on Saturday when Roger Federer will be up against fellow Swiss Stanislas Wawrinka unless he loses heavily to Croatia's Marin Cilic later on Friday.