Shane Lowry knows from personal experience that a four-shot lead starting the final round of a major championship is hardly insurmountable.

Never mind the wicked weather expected to throw an extra layer of uncertainty into the British Open mix on Sunday.

Lowry led by four strokes after 54 holes of the 2016 US Open at Oakmont, but struggled to a closing 76 as Dustin Johnson sauntered to victory.

That experience might serve the Irishman well this time, and he will be metaphorically if not literally carried by fervent support from the Royal Portrush galleries who have adopted him as one of their own.

Only two Australians – Cameron Smith (six under) and Ryan Fox (one under) – remain in the hunt after Jason Day failed to make the cut following a spectacular back-nine collapse

Day joined Adam Scott on the sidelines after missing the British Open cut. Photo: Getty

With polished performer Tommy Fleetwood in second place and the relentless Brooks Koepka lurking seven behind, the engraver will not start etching Lowry’s name into the Claret Jug just yet.

“Who knows when I’ll be in this position again? So, it’s taken me three years to get back here,” Lowry said, making to attempt to downplay the magnitude of the occasion.

“There’s no point in saying to go out and enjoy myself tomorrow because it’s going to be a very stressful and very difficult day.

“I’m going to take the bad shots on the chin and I’m going to take the good shots and try to capitalise on that.

“I’m just going to be myself and play my game and see where it leaves me.”

After perfect scoring conditions on Saturday, dry and calm, rain is expected to arrive late on Sunday morning, and the winds are forecast to blow up to 20 miles per hour (32km/h) by mid-afternoon.

Portrush’s punishing rough is just waiting to gobble up errant shots, a double-bogey or worse awaiting Lowry or anyone else who strays from the fairway.

No lead will be safe

The likelihood that the pace of play will slow as players are buffeted by the wind prompted the R&A to bring the Sunday tee times forward, with Lowry and Fleetwood off in the final pairing at 1.47pm local time (10.47pm AEST).

It will still be a long night for Lowry as he contemplates becoming just the second player from the south of the Irish border to lift a major trophy, after Padraig Harrington who has won three.

“He’s got a big lead but no lead is big enough when the weather gets bad on a links course,” Lee Westwood, who is eight shots behind Lowrt, said.

“He’s going to have an awful lot of pressure on him from the crowd. He’ll be nervous. It’ll be tough, long day for him.

“Last day is always long, but it’s going to be a hundred times worse for him.”

-AAP