Darren Clarke retained his lead to ensure a career-first major victory in the Open at Royal St George's. The 42-year-old Northern Irishman kept his nerves in check to secure a three-stroke victory after a final-round 70. Clarke finished on five under ahead of Phil Mickelson (68) and Dustin Johnson (72). The American duo were followed by Thomas Bjorn (71), of Denmark, at one under and a further trio of Americans, with Rickie Fowler (72), Chad Campbell (69) and Anthony Kim (70) all finshing on level par. Clarke is the UK's first winner of the open since Paul Lawrie in 1999, and becomes the oldest first-time major champion since Roberto Di Vicenzo's in 1967. He had a one-shot lead over Johnson ahead of the final round and showed no sign of nerves as he made certain that the Claret Jug was his. By the final hole, the tournament was Clarke's to lose and he cautiosly made a bogey to become the 2011 Open champion. Clarke said: "It is just incredible. I'm a bit speechless. I played ok today, I did what I had to do and the last few holes when I was far ahead I just tried to be careful and not do anything stupid. "I've been very calm all week, I won six weeks ago and the more you put yourself in winning positions the more comfortable you get. I was very comfortable with my game this week. "I could hear the roars going up for Phil Mickelson on the way round but I was hitting some shots and doing ok. Professional golf has its ebbs and flows, that's the way it goes. "It's very special for me and the kids. They were playing at Royal Portrush today and they will be very proud. "The celebrations could be long and - not arduous - very enjoyable tonight."