HSBC Champions challenge first round leaderboard :
-7 F Molinari (Ita) -6 L Westwood (Eng) -5 Seung-yul Noh (Kor), Y Ikeda (Jpn), H Stenson (Swe)-4 T Woods (US), L Donald (Eng), P Martin (Spa)
Selected others:-3 R Fisher (Eng), P Mickelson (US) -2 I Poulter (Eng), R Goosen (SA), P Harrington (Ire) -1 R McIlroy (NI) level M Kaymer (Ger)
Westwood appears to be enjoying his world number one status
New world number one Lee Westwood is one shot off the lead at the HSBC Champions challenge in Shanghai after firing a first-round, six-under par 66.
The Englishman dropped only one shot and showed no signs of a recent calf injury, or pressure at his new status.
Westwood finished two shots ahead of the man he dethroned, Tiger Woods, who can reclaim the top spot with victory.
Italy's Francesco Molinari was the early pace-setter on seven under after recording a superb 65.
Molinari shot a bogey-free round and made seven birdies, including a run of four straight birdies towards the end, to ensure he finished the day as sole leader, one clear of Westwood and two ahead of Yuta Ikeda, Seung-yul Noh and Henrik Stenson.
But most eyes remained on the battle for the world number one spot, with Westwood eager to retain his place at the top of the rankings having only secured it on Sunday.
I don't think I need to reinforce why I'm number one in the world
And the 37-year-old, playing for the first time in over three weeks after a persistent calf problem, was in excellent form as he picked up shots on some of the toughest holes at Sheshan International. His only dropped shot came at the seventh when he had a clump of mud on his ball in the fairway.
Starting from the 10th hole, the Worksop golfer birdied the 13th, 15th and 16th to reach the turn three under.
He maintained his momentum on his back nine and birdied the first and par-three sixth. Although he bogeyed the seventh, Westwood bounced back to finish with two consecutive birdies.
He said: "I just went out there with a pretty clear mind. I was a little rusty in places with my scoring, but I putted nicely. All in all, I think I probably deserved about a 66.
"I don't think I need to reinforce why I'm number one in the world. I think you get there as a result of having good performances.
"But it's nice to go out there and show everybody that there is a particular reason why I got to that stage."
The task for Westwood is to stay at the top of the pile, with Woods, who lost his number one ranking after a 281-week reign, snapping at his heels after a 68.
The American's round included a run of three consecutive birdies and he is well placed to make a charge that could take him back to the top of the rankings.
It was a performance that left Woods feeling optimistic.
"I hit a lot of good golf shots," said the 34-year-old. "I felt like I was able to control my distance well coming into the greens, and also putted really well."
Westwood has only a narrow lead over Woods and Martin Kaymer, with Phil Mickelson fourth in the rankings.
Mickelson, the defending champion and paired with Westwood, shot a 69 to remain in contention but Germany's Kaymer could only manage level par.