But he soon caught his compatriot at the summit, picking up a shot at the first to move to ten under par.
And Norris took the outright lead when he rolled in his tricky ten-foot birdie putt at the third to get to 11 under before making another gain at the next.
Norris dropped his first shot of the day at the fifth but bounced back in style, reeling off three straight birdies from the seventh to reach 14 under and open up a four-shot lead.
After carding a bogey at the tenth, the 44 year old safely parred the next two holes before notching his seventh birdie of the day at the 13th.
Norris made another bogey on the short 15th but responded with a birdie at the long 17th to head to the 18th tee with a commanding lead.
He then tapped in his par putt at the last to secure the trophy.
"I think it was just our week," said Norris. "Everything aligned and putts dropped and some good shots came, it was amazing.
"I said a couple of years ago when I was about to quit that I didn't want to give it away until I had won a big tournament because I know I can.
"I just tried to stay switched on and not think about the future, things come into your head, you try to block them out. I was really happy with our process today."