Mitchell, watched by his wife Karen and three daughters, saw the 16th hole as the key. Not only did he gain a vital birdie at the difficult, 215-yard hole but also had twos at this hole in each of his first three rounds.
"The hole just suited me," he said. "There were trees left and it was a marker for me because I like to see the ball going left to right."
Mitchell beat David Gilford and the Swede, Jarmo Sandelin, by one shot with Argentinian Eduardo Romero, Sam Torrance and Jonathan Lomas all one shot further back.
Sandelin, who shot 67 yesterday, might easily have won had he not made two mistakes on the final four holes. He was bunkered in two at the 15th and failed to get up and down and then, at the last hole, he three-putted from just off the edge.
Mitchell had previously won the Austrian Open in 1992 and the Madeira Island Open last year. "I enjoyed this win more because I was in front going into the last round and I thought I coped very well," he said.
He three-putted the first hole but that was the only bogey on his card and he birdied the third, fifth, seventh and 16th.