MACK Horton pulled off the ultimate Olympic psyche-out to win Australia’s first gold medal in Rio — then defiantly declared it a win for clean athletes at a Games overshadowed by doping.

Horton overcame Chinese distance superstar Sun Yang in a thrilling grudge match to become Australia’s first 400m freestyle gold medallist since Ian Thorpe and the fireworks continued after the race.

The victory came just hours after Horton had slammed reigning Olympic champ as a “drug cheat” who he does not respect. Sun served a three-month doping ban in 2014.

Horton sensationally claimed after the race the sledge was an intentional tactic inspired by Australia’s Americas Cup-winning skipper John Bertrand.

“It was something I thought of beforehand and it was taking a leaf of John Bertrand’s book,” Horton said.

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“He just referred to racing the American boat as ‘The Red Boat’, so he desensitised from it. Sun is just ‘the drug cheat’ that’s how I went about it.”

Horton said he wouldn’t have outlasted defending champion Sun in a thrilling last-lap duel without the tactic.

“That that last 25, 15m, it felt like I had rocks in my arms basically,” he said.

Australia's Mack Horton pipped Sun Yang to win the men’s 400m freestyle final. Picture: Phil Hillyard Source: News Corp Australia

“But then I kind of flashed back to my statement this morning and thought, ‘I don’t have a choice, I can’t let him beat me now’, so that’s what I did.”

‘A WIN FOR CLEAN ATHLETES’

Horton’s sledge came from a place of truth and he refused to back down under fire from Chinese media after the race.

The tension between the pair was evident before and after the race. Sun stormed off the pool deck after surrendering his Olympic title and the pair’s handshake on the medal dais looked half-hearted at best.

Things got even more awkward when the pair had to sit next to each other at the official press conference and speak about the issue.

Horton, though, stood firm. Asked by an emotional Chinese journalist “why you used those words” to describe Sun, the 20-year-old Australia’s response was blunt.

“I used the words drug cheat because he tested positive “

Horton also said he beef with Sun was not personal but that “he’s one of the athletes here who has tested positive.”

Australia’s Mack Horton won his country’s first gold medal in Rio. Source: Getty Images

Asked earlier whether it was a win for clean athletes, the 20-year-old Victorian said: “You took the words out of my mouth.

“..There’s a lot that goes on behind the scenes talking about drugs in sport but no athlete has really come forward and said it.

“I guess I wouldn’t really feel right if I raced at this stage against something that tested positive and didn’t bring it up.

“It’s the first day of competition. hopefully now people will follow.”

SUN DEFIANT

Sun tested positive for the banned stimulant trimetazidine and was banned for three months by his national swimming association. He claimed it was prescribed by a doctor to treat heart palpitations and was unaware that it had been newly added to the World Anti-Doping Agency’s banned list four months earlier.

The dual London Olympic gold medallist refused to get into a slanging match with Horton but demanded respect.

“I don’t think we need more explanation, I am clean. I’ve done whatever it takes to prove I am a clean athlete,” he said.

“All the athletes here need to be respected. Each country has their own internal affairs. We’re here to compete, we’re here to perform.”

“I don’t think we need to talk about the Australian swimmer’s comments.”

MACK PLANS ANOTHER ATTACK

After completing his emergence as Australia’s first great distance swimmer since Thorpe and Grant Hackett, Horton now has his sights set on the nation’s beloved 1500m freestyle.

He’ll go head-to-head with Sun again, along with Italian gold medal favourite Gregorio Paltrinieri, in what was originally his pet event.

In the meantime, he hopes he and the women’s 4x100m freestyle successes on opening night will set the tone for a historic golden blitz for Australia in Brazil.

“It’s pretty insane, it hasn’t really sunk in,” said Horton who in 3:41.55 — shy of Thorpe 2002 Australian record of 3:40.08.

“Hopefully this can help set up the swim team, this team has a lot to give and I’m really looking forward to what everyone can give.”