Novak Djokovic made a superb start to his ATP Finals campaign with a dominant 6-2 6-1 triumph over tournament debutant Matteo Berrettini.
In the first match of this year's season finale, Djokovic – who is aiming to oust Rafael Nadal as world number one after he was dethroned by the Spaniard earlier this week – made a statement of intent in the Bjorn Borg group.
Five successive, clinical breaks of serve saw last year's runner up – a four-time champion at the O2 Arena – ease to an emphatic victory in just 63 minutes.
Berrettini, the last player to qualifier for the finals, walked towards the wrong exit after Djokovic's win was sealed on a first match point, and given the beating he had just taken, it was perhaps no surprise the Italian seemed slightly shocked.
"It feels great to be back in, earlier this year I had a great stay in London, played well at Wimbledon," Djokovic told BBC Sport.
"Over the years I've played really well in this arena. I've been enjoying it very much.
"It's not easy for Matteo, playing his first tour finals match, I knew he'd be a bit more nervous at the beginning, I tried to use my experience.
"I was fortunate to get the break midway through the first set. He's got big weapons with his serve and forehand but I managed to play really solid."
Djokovic beat Roger Federer in a Wimbledon final for the ages in his last appearance in London, and the Serbian was swiftly into his rhythm against world number eight Berrettini.
Having not dropped a point in the opening game, the 32-year-old forced Berrettini to deuce on his first serve before two breaks handed him the set.
Berrettini claimed a brilliant point in game two of the second set, managing to reach for a low backhand that Djokovic could only skew into the air, providing his opponent with a simple volley.
But it merely stalled Djokovic's process for a brief moment – Berrettini, who is renowned for his powerful serves, going 2-0 and a break down.
Another break for Djokovic followed, though Berrettini did capitalise on the only break point he was afforded.
It mattered little, however, Djokovic getting the better of his opponent's serve once more before rounding off the win with a controlled cross-court forehand.