Robertson heads England's Paul Eales by three shots, who carded a 7-under-par 65, and a group of seven players on 6-under-par 66.
Robertson's round consisted of just 22 putts, which was the key to his day in slightly easier conditions than the players are normally used to at the Houghton layout.
'The course is a little less fiery because the rough is not as bad as in previous years,' Robertson said. 'I'm delighted to have shot such a low score. You never set any great expectations on the first day of a new season; you just take it shot by shot.
'I holed everything today. It was the finest putting display I've ever put on in a tournament. The scary thing is that it could have been 18 putts, but I'm just delighted with the way it started.'
The morning field saw a host of 6-under scores being posted, and for a while it seemed that it would be the mark for the day. But Robertson shot nines of 31 and 31 to surpass the previous record of 63 held by South Africa's David Frost.
Robertson started on the back nine and had birdies on the 11th, 12th, 15th 16th and 18th.
'I just wanted to keep it together on my second nine but the putts continued to drop,' Robertson said.
A par on the first was followed by a 20-foot putt for birdie on the second to move him to 6-under, which tied the lead. A further par on the par-five third was a precursor to a run of three consecutive birdies from the fourth to the sixth that moved him into a commanding three-shot lead.
Robertson added a tricky 10-foot downhill putt for birdie on the par-three eighth to move to 10-under-par - and the record score in relation to par.
Earlier, former amateur prodigy Justin Rose was one of the men to post a 66, along with fellow Englishman Paul Broadhurst, who was playing his first competitive round of golf for 10 months after a wrist injury.
Nick Faldo, one of the pre-tournament favorites, returned a 4-under par 68 to leave him well placed heading into the second round.
The only South African to feature in the top three positions was Roodepoort professional Ashley Roestoff, who also posted a 66. Fellow South African Des Terblanche aced the par-3 12th with a soft nine-iron that pitched less than a foot past the hole and spun back in. It moved him to 5-under par, but he immediately dropped on the 13th before a double bogey on the 14th ended his momentum. Terblanche managed to birdie the final two holes to return a useful 68.
Mark McNulty, winner of the South African Masters at the Wild Coast a week ago, carded a 5-under-par 67, while Retief Goosen finished on a disappointing 1-over par 73.