The Walkinshaw Andretti United driver was a late substitution from Sweden’s Mattias Ekstrom, who fell ill in the days leading up to the event at Sydney’s Accor Stadium.
Mostert defeated a star-studded list of drivers in the group phase and knockout finals including Valtteri Bottas, Kurt Busch, Sebastian Vettel and fellow Supercars star Will Brown.
The two-time Bathurst 1000 winner faced Sebastien Loeb in the final in which he came up fractionally short of taking the decider to a tiebreaker.
“I was shocked to get out of the first group,” said Mostert after getting out of his rallycross car.
“Man, I love driving these cars on this track. After yesterday’s effort, I didn’t think I was a chance, but after making the final I’m an automatic entry, hey?”
Asked during the post-event press conference whether he would like a Race of Champions return, event co-founder Frederic Johnsson interjected before Mostert could reply.
“He should have won, he would have been guaranteed,” Johnsson joked.
Mostert thanked Johnsson for the last-minute invite, which was facilitated in part by Speedcafe founder and event media manager Brett Murray.
“I’m just honoured to be invited once and this was fantastic,” said the 32-year-old.
“I must say, I felt like I probably had the home track advantage because I had the Aussie fans here really amping us up and that we feel that energy as Supercar drivers, even when we have our Supercar rounds.
“This discipline was really different for us, and no doubt next time we’d do it, we’d feel like we’d be more comfortable. But if we went to the ice or the snow, it’d be like a penguin on the beach at Bondi or something just completely out of its element.
“So, we’ll see what happens and where ROC ends up, but like I said, so honoured that Frederic and especially Crusher [Brett Murray] just sitting at the back there. He was a big reason why I’m here as well as a last-minute call-up. So thank you so much.”
Mostert was supported from the sidelines by fellow Supercars drivers Will Brown and Brodie Kostecki. The Dick Johnson Racing driver was on his feet to hype up the Sydney crowd as Mostert and Loeb lined up on the grid.
“When I came off of the rally car, I was thinking ‘OK, how many buttons have I got to push here, and a handbrake and loads of clutch’ and I looked down and I think I saw the big screen,” Monster recounted.
“I saw Brodie giving them the big ones, and he actually has a very unique big one – as we saw on the driver parade. So it was really cool.”
Mostert said he, Brown, and Kostecki took the chance to meet with fans before the racing began on Saturday night.
“We tried to come out of the tunnel before the event and come see the Aussie fans because our sport and what we do is not possible without them,” he said.
“To be able to do what we do, we know it’s not even a dream if we don’t have awesome fans that love motor racing.”
The Supercars drivers will continue their season at the Formula 1 Australian Grand Prix on March 13-16.
