Murray feels the love of the fans as No.1 hits top gear
Andy Murray received a standing ovation after marking his first match as world number one with victory over Marin Cilic at the ATP World Tour Finals.
The O2 Arena was certainly a fitting stage for Murray officially to step out on top of the world for the first time and he kept his winning run going with a comfortable 6-3 6-2 victory.
That made it 20 successive wins for the Scot, who needs to match Novak Djokovic's performance this week to ensure he holds onto the ranking until the end of the year.
Djokovic won his opening match against Dominic Thiem on Sunday and Murray knew he could not afford any slip-ups.
The 29-year-old said: "It was a great atmosphere in here. I played one of my best matches that I've played here and I'll just try to keep it going until the end of the year."
A tally of two winners and 14 unforced errors in the opening set was hardly world-leading stuff but it was good enough for Cilic, whose garish shorts were more memorable than his shots.
By the end, Murray was playing some fine tennis - and victory over Kei Nishikori tomorrow would very likely be enough for a first semi-final appearance here since 2012.
The international nature of the crowd at the O2 means it has not always felt like a home event for Murray - but there was no doubting who the favourite was this time.
The arena was on its feet when Murray was announced as the world number one.
Murray was taking on the lowest-ranked player in his group but victory was not a formality, particularly considering Murray's surprisingly poor record here.
Cilic arguably came into the tournament as the most in-form player in the world behind Murray, having won a title in Basle last month and then claimed a first win in 15 against Djokovic at the Paris Masters.
The Croatian, who is working with Murray's former assistant coach Jonas Bjorkman, also won his most recent meeting with the Scot in Cincinnati in August.
Neither man hit any great heights in the opening set but it was Murray who took most of his chances.
After saving break points in the opening game, he had the better of three successive breaks and then held for 4-1 despite serving two double faults.
Nerves would have been understandable but there were enough errors from his opponent for him to hold onto his advantage and take the opening set.
Cilic possesses both power and very good movement for a man of 6ft 6in, but Murray is the master of making life awkward for tall opponents.
He was beginning to play more like the man who has won his last four tournaments and a forehand winner earned him the first break of the second set and a 3-2 lead.
Cilic simply had no answer now and Murray wrapped up victory in an hour and a half when Cilic netted a forehand.
In the earlier match, Stan Wawrinka's hopes both of finishing the year ranked three and of reaching a fourth straight semi-final at the O2 were dealt a major blow by defeat to Nishikori.
Milos Raonic, a confident winner over Gael Monfils on Sunday, is now in pole position to be best of the rest behind Murray and Djokovic, with Nishikori closing fast.
Wawrinka has played some fine matches here, most memorably his tense semi-final against Roger Federer in 2014 - but this was not one of them and he was well beaten 6-2 6-3.
The 31-year-old has been troubled by a knee problem, and he said: "It was not a great match compared to what I can do.
"I was a little bit slow on everything. I was hesitating a lot with my game, my movement.
"I'm sure I still have something inside me to play some great tennis before the end of the year."