Andy Murray enjoying home comforts in London

Murray replaced Novak Djokovic atop the world rankings last week and, in his first match since then, beat Cilic 6-3 6-2 to the delight of most of the 17,000 spectators at the O2 Arena.

The Brit was made to work hard during a first set in which he made just two winners compared to 14 unforced errors but warmed up to his task to put himself in pole position to qualify from Group John McEnroe.

The 29-year-old is looking to hold off the challenge of Djokovic at the event to retain world No.1 status and the partisan support could well be a crucial weapon in doing that.

"Obviously it was a great atmosphere out here with pretty much a full house and it was fantastic," said Murray.

"I played one of my best matches that I've played at this venue over the years, so I'll just try to keep going until the end of the year.

"A big thank you for all of the support – it was an incredible atmosphere and I really, really appreciate it.

"I keep working hard to give the fans moments like this on the court and I hope they keep enjoying it."

Murray saved a break point with an ace early in the second set and went on to break Cilic with the score at 2-2, before doing the same at 4-2.

It was a 20th win in a row for the two-time Olympic champion and as he gears up to face Kei Nishikori, who earlier beat Stan Wawrinka in straight sets, on Wednesday, he couldn't be feeling better about his current game.

"When you start winning matches you gain confidence and on the important moments, like the break points, I was a little bit more solid than Marin," added Murray.

"He had some chances in the first set and at the beginning of the second set but when I had my opportunities, I took them and that's what winning matches does for you."