Unfancied Australian Brad Kennedy is refusing to think about making the halfway cut despite storming the leaderboard with a birdie-filled British Open start.

Unfancied Brad Kennedy insists it's too early to dream of making his first major championship cut despite tearing up St Andrews with a first-round birdie blitz.

One of 11 Australians in the 153-man field for the celebratory 150th British Open, Kennedy upstaged them all but Cameron Smith with a four-under-par 68 on Thursday.

The 48-year-old bagged eight birdies to also out-do his esteemed playing partner, two-time Open champion Ernie Els, with the equal-fifth lowest first round.

"I didn't expect that today," Kennedy said after matching the likes of world No.1 Scottie Scheffler, former top dogs Dustin Johnson and Lee Westwood and young guns Talor Gooch and Viktor Hovland.

"We had a really nice breeze early on this morning and I managed to hit some great iron shots in to some tough pins."

The world No.135 dropped successive shots on holes eight and nine but never lost focus to give himself a fabulous chance of earning a first-time weekend tee spot after missing the Open halfway cut in his three previous starts.

"No, I've still got a lot of work to do. That's way out of my idea of what I want to do," said Kennedy, still wary after missing the cut last year even after opening with a solid 71 at Royal St George's.

"I've been playing nicely in Japan, had a couple of nice weeks' rest back home and I really wanted to come out and see how far I could push myself in terms of what shots I hit and how I hit them.

"The imagination really needs to come out on some of these holes. So I'm really happy with the progress so far.

"I played great most of the day. Only hit one or two poor shots, regrouped after a couple of bogeys on the back nine and played really nice to finish."

A three-time Japanese Tour winner, Kennedy's other most notable victories include twice taking out the New Zealand Open and winning last year's TPS Victoria.