Wimbledon champion Roger Federer will return to London in November having booked his place in the season-ending Nitto ATP Finals.
Federer's record eighth triumph in SW19 saw him qualify for the elite eight-man event which is staged at the O2 Arena.
The Swiss is also the record-holder for most titles at the tournament having won it six times.
“I look forward to returning to London in November,” said the 35-year-old. “I was sad not to be able to compete last year (due to injury) as I love playing there and had not missed the event since 2002.”
French Open champion Rafael Nadal had already sealed his place in the field, while six spots remain up for grabs.
Those berths are currently filled by Dominic Thiem, Stan Wawrinka, Wimbledon runner-up Marin Cilic, Alex Zverev, Novak Djokovic and Andy Murray.
This year's tournament takes place from November 12-19.
Get exclusive Willie Mullins insight, plus access to premium articles, expert tips and Timeform data, plus more... 
