The ATP Tour World Finals will stay in London until at least 2018, it was confirmed on Thursday night.
London Mayor Boris Johnson announced the news via Twitter having taken part in the draw for the end-of-season event.
"Fantastic news that ATP world tour finals staying in Ldn for another 3 years," he tweeted.
1/2 Fantastic news that ATP world tour finals staying in Ldn for another 3 years - still the world's number one sporting city
— Boris Johnson (@MayorofLondon) November 12, 2015
At the launch event for the 2015 edition, ATP executive chairman Chris Kermode confirmed the new deal.
"We are delighted to have reached an agreement which will see the tournament celebrate its 10th successive year in London in 2018," said Kermode.
There had been speculation that the Finals could return to Asia or shift to continental Europe, but Kermode indicated that London's track record of success meant it deserved to keep the event.
"The tournament has been a spectacular success since moving to The O2 in 2009, generating record crowds, incredible atmospheres, and a soaring worldwide TV audience which broke the 100 million mark for the first time last year," he said.
"The O2 has enabled us to present the sport in a new and vibrant way, in a media-friendly time zone, and in one of the world's greatest cities. For us, there is currently no better place to stage our season-ending event."
Tracey Crouch, Minister for Sport, said: "The Barclays ATP World Tour Finals have been a fantastic success in London and I am delighted that it will continue to be hosted in the capital. Staging this tournament featuring the very best players in the world not only provides an important boost to the local economy but can also help inspire future generations of tennis players, therefore growing the sport in Britain."
Earlier at City Hall, Mr. Johnson helped Andy Murray avoid world No.1 Novak Djokovic, as the home favourite was drawn alongside David Ferrer, Rafael Nadal and Stan Wawrinka in the Ilie Nastase group.
Defending champion Djokovic, meanwhile, will play in the Stan Smith group against six-time winner Roger Federer, Tomas Berdych and Kie Nishikori.
Djokovic is the clear favourite for the tournament, having won 10 Tour events this season and three grand slams, while he won this event a year ago.
"This has been, by far, the most successful season of my life and I just try to better it," he said.
Murray had initially been linked with skipping the event in favour of preparing for Great Britain's Davis Cup Final against Belgium, but will now go up against fit-again Nadal, Warwinka and Ferrer.
"I haven't played against Stan for a long time. All the matches are tough ones but there should be some tough ones too," he said.
"I feel good, I feel fresh and hopefully I can play some good tennis this week."
Murray's brother Jamie was paired with the Bryan brothers alongside regular partner John Peers.
The Finals start at London's O2 on Sunday, with Djokovic opening up against Nishikori, with Murray facing Ferrer on Monday.