Andy Murray
Murray was given a decent workout before completing victory in his ATP Fianla opener. Getty Images

Andy Murray began his reign as world number one with an impressive straight sets victory over Marin Cilic at the ATP World Tour Finals at The O2 Arena. In his first match as the official king of men's tennis the Wimbledon and Olympic champion claimed a 6-3 6-2 win over Cilic whose wait goes on for success at the season-ending tour finals in London.

In an opening set littered with errors it was Murray who was able to show the greater consistency with the Croatian Cilic unable to hurt the Scot sufficiently with his solid groundstrokes. The number seven seed recaptured his best at the start of the second, yet Murray was unmoved and he completed a 20th victory in a row which despite a one-sided nature of the score was far from routine.

Murray will face Kei Nishikori in his second match on Wednesday [16 November] after the Japan number crushing an out-of-sorts Stanislas Wawrinka in the opening match in the John McEnroe group. Victory will all but secure his place in the last four and keep him on course to hold off Novak Djokovic and secure the year-end world number one.

"Obviously it was a great atmosphere, pretty much a full house and I played one the best match here over the years," Murray, who is seeking his first title at the ATP Finals. "I'll try and keep it going until the end of the year. It was an incredible atmosphere today. I'll keep working hard to keep giving you moments out on the court

"When you start winning matches and in big moments I was a little bit more solid than Marin. He had chances at the start of the first set and the start of the second set but when I had my opportunities I took them and that is what winning matches does for you."

Though wins for Djokovic, Milos Raonic and Nishikori had kicked off the singles competition in Greenwich in the opening three sessions, the curtain would truly come up on the tournament upon the arrival of the new world number one. Murray was given an ovation fitting of his breakthrough achievement but knew he would likely have to break new ground to make the ranking stick beyond this week.

Opponent Cilic could also be forgiven for being distracted by events largely beyond his control also, ahead of next week's Davis Cup final where he will spearhead Croatia's attempts to beat Argentina. Though Murray had won his last 19 matches, his last loss came against the 28-year-old Cilic in the Cincinnati Masters final, while the presence of the Brit's former coach Jonas Bjorkman in his corner was a boost for the 2014 US Open champion.

Initially at least, Cilic's power proved too good for Murray's usually impeccable defence but the world number seven was unable to convert two chances to break in the opening game. Murray took full advantage of the early reprieve and broke himself for a 2-0 lead as Cilic's backhand collapsed under scrutiny.

The break triggered a run of three in a row, to allow Murray to keep his lead yet ensured the opening exchanges were underlined by a series of scrappy points from two of the top eight players. The Dunblane player needed an ace in the fifth game to keep the lead, after another two double faults opened the door again for Cilic.

Though Murray was dictating, the contest remained attritional with errors flowing from both players' rackets. Cilic produced the first love service game but it paled into insignificance as the three-time major champion took the opening set with a chance-less hold of his own.

The blows being inflicted by both players continued to be seismic at the start of the second set, with the psychological warfare between the two providing the subtext for a bruising encounter. Cilic missed the chance to convert a period of dominance into a break, and Murray responded with two thumping forehand winners to break himself at 3-2.

Cilic was forced to go on the offensive but instead the approach led to his downfall as he went long on the forehand side, giving Murray a double-break and a win which sees him match Djokovic's success over Dominic Thiem in the fight to end the season atop of the ATP rankings.