Appropriately, the two standout performers clashed in the final after 21-year-old Greek debutant Tsitsipas eclipsed six-time champion Roger Federer and Austrian Thiem dispatched defending champion Alexander Zverev.

The first-time finalists' technicolour games lit up the O2 Arena as the tournament reached its climax with Tsitsipas looking to become the youngest winner of the tournament since a 20-year-old Lleyton Hewitt was victorious in 2001, and youngest debutant to lift the trophy since John McEnroe back in 1978, while Thiem was aiming to win his sixth ATP title of 2019.

But it was Tsitsipas who sealed a sensational win 6-7 (6-8) 6-2 7-6 (7-4) at the prestigious season-ending tournament.

This was only the third time since 2002 that at least one of Federer, Rafael Nadal or Novak Djokovic have not reached the final and while it may not signal a changing of the guard, the week has felt like a momentum shift for the new generation.