FINAL ROUND LEADERBOARD:
Westwood moved away over the final three holes
(GB unless stated)
-15 L Westwood
-10 I Poulter
-9 M Foster
-7 F Andersson Hed (Swe), M Campbell (NZ), N Fasth (Swe), MA Jimenez (Spa), S Kjeldsen (Den), Z Scotland, S Walker
-6 N Dougherty
-4 C Montgomerie
-2 J Van de Velde (Fra)
+2 R McIlroy
Lee Westwood fired a closing 65 to claim the British Masters by five shots at The Belfry.
After battling Ian Poulter and Mark Foster for most of the day, Westwood surged away with a 30-foot putt on the 16th and then eagled the 17th.
The former European number one ended 15 under, with Poulter (70) in second and Foster third on nine under after a hook out of bounds on the 13th in a 73.
"It was a great finish and I hardly put a foot wrong," said Westwood, 34.
"Obviously the 16th and 17th killed off anybody else's chances. I holed one like that on 16 against Tiger (Woods) in the Ryder Cup. The eagle then put the icing on the cake."
It was Westwood's second title this season and 18th European Tour success.
Eight-time European champion Colin Montgomerie ended on four under after carding a final-round 74.
Northern Ireland's Rory McIlroy, who came to prominence as an amateur at the Open, leaked five bogeys in six holes on his front nine before battling back to a 73 to end two over in his first professional tournament.