South Australian Nick Cullen is proving his first round lead in the Australian Masters is no fluke with a barnstorming start to his second round at Royal Melbourne.

Cullen, who only turned professional four years ago, fired an opening round six-under for a two-shot overnight lead over defending champion world No.2 Adam Scott and young German Max Kieffer.

But Cullen, 29, has used ideal conditions to further increase his lead and after two opening birdies is out to eight-under after five holes.

Cullen is the twin brother of cricketer Dan, an off-spin bowler who has represented Australia at Test and one-day level.

He posted his maiden professional win in last year’s Indonesia Open and won the Queensland Open three months ago.

Scott and Kieffer don’t tee off until just after midday but there have been some early movers on the leaderboard.

Victorian Matthew Griffin, playing in the same group as Cullen, started the day at two-under but has nailed four birdies to sit at six-under after five holes.

Queenslander Brett Rankin has picked up two shots to move to five under after five holes.

Jarrod Lyle, making his return to competition after battling cancer, remains steady at one over after two holes.