Watts Up Partytime has stunned punters twice in one night, winning both the heats and the final of the Group 1 $250,000 Yabby Dam Farms Great Southern Star at massive odds.

The Andy Gath-trained squaregaiter took out the heat in at an opening quote of $26 before a powerful performance to outrun Inter Dominion winner The Locomotive at $81 to give the master trainer his fifth Great Southern Star victory.

“Not in our wildest dreams did we think he would win it,” Gath said.

“Some of the others were expected, I saw him three fence and saw him travelling and thought we would be really unlucky, but he is just a short course specialist – he is a lovely horse.

Driver Kate Gath couldn’t believe her luck winning the Group 1 feature for the trotters on Sportsbet A.G. Hunter Cup night.

“What an outstanding effort by the little fella and I didn’t see this happening tonight,” Kate Gath said.

The short priced $1.25 favourite The Locomotive finished second while the Marg and Paddy Lee-prepared Keayang Chucky rounded out the placings.