SYDNEY, Dec 9, 2012 (AFP) - The 53-year-old Australian held his game together after a three-hour wind delay to post a dogged par 72 final round to win his second Stonehaven Cup at four-under 284 from compatriot Brendan Jones (71).
Another Australian, Cameron Percy (73), was third, with English world number four Justin Rose in a group of three golfers at one-under.
Senior's second Open victory came 23 years after his first national open triumph in 1989.
The previous oldest Open winner was five-time British Open champion Peter Thomson at 43 at South Australia's Kooyonga in 1972.
"I'm getting a bit long in the tooth now. I really thought these days were over," Senior said.
"God, golf is such a funny game. One minute you think you're down, the next minute you're up. This is probably the most special.
"I can't believe how many people stuck it out. I would have been at home in bed by now," he said after the tournament finished in near darkness following the lengthy delay.
As virtually the entire field went backwards in winds gusting up to 80 kilometres an hour (50mph), Senior dropped just two shots all day, at the fifth and seventh holes.
Birdies on the par-4 10th and 12th holes proved decisive.
Japan-based Jones almost snatched victory with a spectacular finish.
In his first national championship in four years, Jones nearly overcame a 12-shot deficit early in his round after going five under through his last 13 holes.
Featuring a brilliant eagle on the par-5 17th, Jones eventually closed with a 71 to finish with a 72-hole total of three-under 285.
Rose, who led during the final round, stuttered with bogeys at the 16th and 18th holes to drop back, while Australia's world number seven Adam Scott finished tied for 14th at two-over 290.
Tournament director Trevor Herden said officials had no alternative but to halt proceedings just before noon when fierce winds knocked over a television tower near the 18th green.
The wind change also caused scoreboards to topple over, balls to move on the fairways and greens and sand to be blown from bunkers and into the galleries.
Herden said player and spectator safety was paramount.
Scores after the final round of the OneAsia co-sanctioned Australian Open at the par-72 The Lakes course on Sunday (Australia unless stated):
284 - Peter Senior 75-68-69-72
285 - Brendan Jones 68-71-75-71
286 - Cameron Percy 72-69-72-73
287 - Kim Felton 68-75-72-72, Kieran Pratt 71-71-70-75, Justin Rose (ENG) 68-73-70-76
288 - Michael Hendry (NZL) 72-71-74-71, Scott Gardiner 76-71-68-73, Stuart Appleby 70-73-70-75
289 - Brett Rumford 73-69-75-72, Nick O'Hern 71-73-73-72, Rodney Pampling 74-69-73-73, Matthew Jones 71-72-69-77
290 - Cameron Smith 72-74-69-75, Steven Jones 73-68-73-76, Mathew Goggin 71-70-73-76, Adam Scott 72-71-71-76
Selected scores
293 - Tom Watson (USA) 78-68-78-69, Rory Hie (INA) 73-69-75-76, Liang Wen-chong (CHN) 73-71-72-77, Kyle Stanley (USA) 72-71-70-80
302 - Zhou Guo-wu Zhou (CHN) 74-73-74-81