Novak Djokovic
Djokovic will finish as the world No.1 for the third time in four yearsGetty Images/GLYN KIRK

Novak Djokovic secured the year-end world No.1 and qualified for the ATP World Tour Finals last four with a faultless display to knock-out Tomas Berdych in straight sets in London.

The 6-2 6-2 victory sees the Serbian dismiss the challenge of Roger Federer and set up a semi-final meeting with Kei Nishikori after confirming that he will finish top of the men's rankings for the third time in four years.

Berdych's chances of reaching the knock-out stage are over after the heavy loss to Djokovic ensured he could not finish ahead of both Stanislas Wawrinka and Marin Cilic if all three players are tied on one victory each.

A win in two sets for Cilic in the evening session will see qualification for the final semi-final berth decided on games percentage, with Wawrinka requiring just three games to finish above the Croatian even if he loses in straight sets.

At the start of the day all four players in Group A remained in contention to join Federer and Nishikori in Saturday's semi-final in what promised to be a nail-biting final day of round robin competition, with Djokovic and Berdych having the luxury of laying down an early marker ahead of the evening session.

A set for Djokovic would be enough for him to reach the last four for a fifth time while a 30th consecutive victory indoors would secure the year-end world No.1 ahead of Federer.

After beating Cilic on Wednesday, Berdych was seeking a first ever hard court win over Djokovic and one that would put him on the brink of a second semi-final appearance at the season-ending tour finals.

But the world No.7 was stifled from the outset as Djokovic cruised into a double break lead as he exposed Berdych's movement with a combination of solid ground-strokes and deft drop shots.

The two-time Czech Republic Davis Cup winner had lost the first 11 games of his last meeting with Djokovic in Beijing but got on board with his first service hold at the third time of asking, however that did little to deny his opponent who secured the first set and passage to the last four in just 31 minutes.

The one-way traffic continued as the second set followed a similar pattern to the first, with Djokovic powering into a 4-0 lead before Berdych hit back with a solid service game.

However, Djokovic fought off any potential Berdych come back with successive holds to qualify for the semi-final and continue his pursuit of a third title in a row at the O2 Arena.