Day 3: Djokovic v Murray

Sue Barker is at the O2 Arena in London to present live coverage of the ATP World Tour Finals. Roger Federer retained his title last year, proving wrong those who said the Swiss maestro's career was in terminal decline. The 31-year-old continued his excellent form into 2012, winning Wimbledon and regaining his world number one ranking. Now he is aiming to become only the third man to win three season-end championships in a row.