St Andrews: Jason Day is in the box seat to become the first Australian to win The Open since Greg Norman in 1993 after gaining a share of the overnight lead in St Andrews.

The Australian, who only last month collapsed during the US Open after an episode of vertigo, is in a three-way tie at the top of the leaderboard at 12 under with 22-year-old Irish amateur Paul Dunne and 2010 Open Championship winner at St Andrews, Louis Oosthuizen.​

"It was tough with what went on at the US Open, and then even though I wanted to finish a little bit better, I was just glad to get it done," Day said of his bout of vertigo.

"To be able to come back pretty much three weeks later and play the way I've been playing, I know this is one of those events that I haven't really played well in the past. I think my previous best finish here is T30. I mean, it's not my strongest major, and I've always said at the start of this week, I said, I'm looking forward to changing that this week.

"You know, I'm just very happy with how my health has progressed and where it's going, and overall, just I feel healthy and I feel up to the challenge tomorrow. I'm looking forward to an exciting finish, not only for myself but from everyone else."

​It capped off an impressive afternoon from the Australians, with Marc Leishman producing the best round of the tournament – eight under 64 – to finish the day three shots off the lead at nine under.

Fellow Australian Adam Scott was left to rue several missed key putt opportunities, but also sits three shots off the pace alongside Leishman at nine under after a mediocre round of two under, with Steven Bowditch another shot behind.

Day had an eight foot birdie putt on the 18th for a chance to take the outright lead into the clubhouse, but t​he 27-year-old was unable to capitalise.

However the miss has set up a dream final round pairing with tournament favourite and man-of-the-moment Jordan Spieth, who is going in search of his third consecutive major of the year.

"I'd be very shocked if he's not around in contention going up the last few holes," Day said of Spieth.

"I think that he's very – even though he's 21 – he's very mature for his age and he's very patient with himself, and he putts better than everyone else. He's definitely going to be the favourite, but I mean, I still have a lot of fans out there that are supporting me along the way. I hear the Aussies in the crowds and I even hear the locals here, even people that aren't from the UK are supporting me.

"There's going to be a lot of people out tomorrow that are supporting either myself or Jordan, and it's kind of a neat experience. I'm definitely going to try and fly under the radar, but it's hard to when you're in the last two groups of the championship playing the last round. The more times I put myself here, the more times I want to be here, and hopefully over time I start to change that, and hopefully through winning more of these tournaments, I start to become the heavy favourite, and that's what I ultimately want."

THE LEADERBOARD

-12 Paul Dunne (a)
      Louis Oosthuizen
      Jason Day
-11 Jordan Spieth
​-10 Padraig Harrington
-9   Marc Leishman
      Jordan Niebrugge (a)
      Sergio Garcia
      Justin Rose
      Retief Goosen
      Robert Streb
      Adam Scott
      Zach Johnson
      Danny Willett 
-8   Steven Bowditch