Mostert started from fourth on the grid and escaped unharmed from early pit lane contact before charging to the front in the middle phase of the race.

He then had to chase down an off-strategy Kai Allen and David Reynolds in the closing stages to take the win and the Semi-Final spot that comes with it.

Mostert was joined on the podium by Broc Feeney and Allen, while Reynolds fell to 14th after being forced to pit for fuel three laps from the finish.

Feeney is now locked into the Semi-Final based on points, leaving just five spots to be decided on Sunday.

“I can’t believe it to be honest,” said Mostert.

“It’s been an up and down year, but we found our form here right at the right time. We’ve generally been pretty good on these tracks, I’m just lost for words.”

It was a sweet and sour day for WAU as polesitter Ryan Wood’s championship hopes suffered a major blow.

The early leader lost places to Feeney, Matt Payne and Mostert in quick succession before being called to pit lane on lap eight with what turned out to be a fuel leak.

‘Just gut-wrenching’: Bizarre issue strikes Wood at GC500

Wood received regular service and was sent on his way, but was back in just laps later thanks to a mechanical black flag – this time required to go to the garage.

The race’s first Safety Car was called soon after as officials needed to attend to signage that had come adrift from the catch fencing at Turn 1.

That triggered a rush to the pit lane on lap 12 and chaos unfolded as teams opted to double-stack their cars.

Feeney took his stop untroubled, but behind Mostert became stuck behind Allen – who was in turn waiting for teammate Payne.

Mostert pushed and shoved until Allen moved out of the way but was then collected by Payne as the Kiwi emerged from the Grove pit box.

The result was Feeney leading from Cam Waters (who gained four places in the chaos), Mostert and Payne, who was issued a 15-second penalty to serve later on.

The restart was followed almost immediately by another Safety Car period as a tyre failure – caused by earlier contact – put Cooper Murray into the wall at the beach chicane.

A luckless Jaxon Evans also took damage after being collected by a stray wheel from the Erebus Camaro.

Erebus rookie Cooper Murray explains Gold Coast 500 crash

Waters put Feeney under major pressure on the restart, but the battle was again interrupted by the Safety Car, this time to reset the Turn 1 tyre bundle that had been clipped by Mostert.

The WAU driver was the star of the show for the right reasons in the next phase of the race, making impressive Turn 11 overtakes on Waters (lap 38) and Feeney (lap 42) to take the lead.

Mostert kept the hammer down and pulled an eight-second lead over Feeney by the time the Red Bull Ampol Camaro came to pit lane for the final time 25 laps from home.

Mostert pitted a lap later and rejoined with a similar margin to Feeney but 12 seconds behind Reynolds and Allen.

They were among a handful to have topped off on fuel under the third Safety Car period, taking a gamble that they could make it to the flag without another stop.

Mostert continued to charge and overtook Allen for second with 15 to go, by which point Reynolds was less than two seconds up the road and still conserving fuel.

It took just three laps for Mostert to reel in and overtake the Team 18 Camaro, eventually taking the flag 7.6s ahead of second-placed Feeney.

The Finals Series standings after Gold Coast 500 opener

Allen hung on for third ahead of Waters, who clipped the beach chicane exit wall late but continued untroubled.

Will Brown salvaged fifth from a day in which a major crash in the Top 10 Shootout required rushed repairs.

Brown fell to the back in the early laps following contact from Allen, and survived later incidents with Will Davison and Aaron Cameron on his way to fifth.

Sixth through 10th at the flag were Anton De Pasquale, James Courtney, Andre Heimgartner, Thomas Randle and Payne.

Payne was shuffled back in a wild late-race battle that included contact with Davison, who fell from ninth to 13th thanks to a resulting five-second time penalty.

That ended a horror day for Dick Johnson Racing, with Brodie Kostecki a non-starter following his crash in qualifying.

Results: Repco Supercars Championship Boost Mobile Gold Coast 500, Race 1