Sue Barker presents live coverage of Roger Federer v Jack Sock on the opening day of the ATP World Tour Finals.

London's O2 Arena is once again the host for the thrilling finale to the men's tennis season in which the top eight players in the world go head to head.

This time in 2016, Andy Murray beat five-time champion Novak Djokovic to win his first ATP World Tour Finals title and end 2016 as the world number one. Show less