The eight-player singles field for the tournament is now set, with both David Ferrer and Kei Nishikori assured of their places at the season finale.
They join defending champion Novak Djokovic, Andy Murray, six-time winner Roger Federer, Stan Wawrinka, Tomas Berdych and Rafael Nadal for the contest.
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Staged from Sunday 15 November to the following Sunday, players will compete in a minimum of three matches each during the group stages as they battle for a place in the knockout semi-finals.
Djokovic is odds-on favourite to win the tournament, but Andy Murray (12/1) and Rafa Nadal (20/1) are surely tempting prices if you fancy a flutter.
Afternoon sessions from noon, Sunday, November 15-22, £50-£2,500, The O2 arena