The Worksop man, who turned 39 on Tuesday, retained the title he won last year after a blistering start.
A shaky end to his tournament added tension, as he battled the stifling heat and fatigue – playing 32 holes on the Sunday due to weather delays – but in the end he won by two shots.
Speaking after lifting the trophy he said: “Today was hard. It is never easy playing in these conditions and I had to play 32 holes.”
“I was really feeling it on the back nine. When you are in contention and under pressure, it seems to zap your energy faster.”
Westwood was very much the favourite for the tournament, and said that added pressure.
But he hopes the victory will spur him on to even greater things in 2012.
“Hopefully I can go on and win other tournaments,” he said.
“It is tough when you are the favourite because if you don’t win then it will be disappointing.”
His opening round of 65 included nine birdies set the pattern for the week.
Westwood followed this with a faultless 68 on Friday to maintain the lead, but only managed four holes on Saturday as a long delay for lightning saw the players return to the clubhouse.
This meant Sunday held the prospect of 32 holes in high temperatures and humidity.
Having birdied two holes on Saturday he went on to post seven more in another round of 65.
With a big lead going into the final round, it looked like he would retain his title with ease but a two over par 74 saw him win by just two shots.
This gave him his 38th tour victory worldwide.