It seems Joao Moreira is in an impossible position but Zac Purton knows his rival still has some tricks up his sleeve and won’t rest until it is mathematically impossible for the Magic Man to steal the 2017-18 jockeys’ championship from his grasp.

Purton’s double at Happy Valley on Wednesday night pulled him four clear in the championship but because the Australian holds a clear advantage in the number of seconds – which will be used to separate the pair in the event of a tie – the lead is essentially five.

That means Moreira needs to win five more races than Purton at Sunday’s season finale at Sha Tin and while that seems a tall order, even on an 11-race card, Purton has seen “Magic happen” before.

It was the 2012 International Jockeys’ Championship at Happy Valley and Purton looked like he had the title in the bag as Chancellor stormed to the front in the final leg.

Zac Purton has one hand on the jockeys’ championship

Only a win on Noble Deluxe would clinch it for the then Singapore-based Moreira and when Purton shoved his rival back into a pocket at the 300m the race looked over.

We’ll let Purton take the story from here.

“I still have it in my memory when he launched like a ghost, like he used to be called in his homeland, and pipped me,” he said of Moreira’s desperate dive for the line, after dramatically switching off Chancellor’s heels with 200m to go. “So on Sunday I want the post to come as quick as it can.”

Purton has a terrific chance to extend his lead to what would be an almost unassailable five-win margin in the opening event aboard Best Effort and in the process help Almond Lee collect a crucial 16th winner.

The personal glory of a premiership is one thing, but losing your livelihood is another, and that is the situation facing Lee if he doesn’t win a race on Sunday.

Four-all: Zac Purton and Joao Moreira trade blows in titanic battle at Sha Tin

Best Effort hasn’t won on the turf since February last year and while the grey has been campaigning on the dirt this season, he showed enough spark last start to suggest he could be competitive back on the grass in the Class Five Medic Kingdom Handicap (1,800m).

Lee has eight runners and perhaps his best chance is consistent four-year-old Enjoy Life in the Class Four All You Wish Handicap (1,400m).

The two biggest head-to-head battles between Purton and Moreira come late in the day in the two highest-class races.

In the Class One Sha Tin Mile Trophy (1,600m), Purton’s Rise High and Moreira’s Doctor Geoff both look horses with considerable upside.

The four-year-old series came too soon for the French-bred Rise High and Caspar Fownes’ patience has paid off with two late-season victories.

The last of those was over the course and distance over 1,600m over Doctor Geoff and carrying nine pounds more than his rival.

A subsequent win by Doctor Geoff at Happy Valley means they now meet with a 10-pound weight swing to Rise High.

If the championship does come down to the 808th and final race of the season it will be a tantalising tactical clash between Purton on Solar Patch and Moreira on Hezthewonforus.

Solar Patch has drawn one in the Class Two Hong Kong Racehorse Owners Association Trophy (1,400m) and Moreira has to deal with gate 14 on Hezthewonforus.

‘It’s not about the money’: ‘Magic Man’ Joao Moreira reflects on the shock decision that rocked Hong Kong racing

The form around both horses looks strong, with Solar Patch second behind Win Beauty Win two weeks ago and ahead of Conte.

Hezthewonforus seems to have some points in store and has trialled well since his close second behind Simply Brilliant a month ago.