Unflappable Cameron Smith has seized control of the milestone 150th British Open with a second round for the ages.

Smith etched his name in golf's history books after registering a nerveless, bogey-free, eight-under-par 64 to snare a two-stroke lead on Friday.

The world number six's 13-under halfway total broke the St Andrews 36-hole Open scoring record previously shared by Greg Norman, Nick Faldo and Louis Oosthuizen.

Smith, though, will have a swag of the sport's biggest names — including Open favourite Rory McIlroy, Dustin Johnson, world number one Scottie Scheffler and inspired countryman Adam Scott — hunting him down in a mouth-watering weekend shootout at golf's spiritual home.

But after further fuelling hopes of a first Australian winner of the famous Claret Jug since Norman at Royal St George's in 1993, Smith said he had never felt more ready to finally break through for his elusive first major.

"It's just exciting to be leading the Open after a couple of days," he said.

"That experience tomorrow is going to be really cool. There's a lot of Aussies in the crowd, it seems like. Had a lot of support the first couple of days and really can't wait for the next couple.

"It's obviously a really good spot to be in. I feel like I've been in this spot a lot over the past couple of years, and things just haven't quite gone my way yet.

"I've just got to be really patient over the weekend. I think the golf course is going to get a lot harder and a lot faster, so just be patient and make good putts."

As he did all day on Friday.

The scrambling wizard mixed some majestic iron play with a series of masterful long-range two-putts to amass six birdies and a rip-roaring eagle three on the par-five 14th where he rolled in a curving 64-footer to place the field on notice.

At that point, Smith threatened to equal the lowest round in men's major history — Branden Grace's 62 at the Royal Birkdale Open in 2017.