The pair shot 65s to lead by one from Lee Westwood, Robert Rock, Rafael Cabrera Bello and Johan Edfors with three players on five under and 14, including 2004 champion Charl Schwartzel, three off the pace.

Swede Jonzon was especially impressive at the Leopard Creek Golf Club, with two birdies and an eagle in his opening four holes giving him a flying start.

Another birdie on the par-four sixth helped him complete the front nine in 30 – the lowest of the day – and he consolidated that performance with a 35 on the back nine to complete a bogey-free round.

"I played really, really well – especially my shots into the green where I found my speed and the lines on the greens," he said. "It was just a day when you play really well. The weather in the afternoon was also nice. The wind died down and made it quite easy.

"It's just sometimes that days like these happen. It's when you don't think about it when it does happen."

American Mattiace, who lost a play-off to Mike Weir at the Masters in 2003, added: "I really wanted to get off to a good start today.

"I played in a tournament last week in Buenos Aires in Argentina and I really didn't get off to a good start.

"So I wanted to go around and shoot a really low score and I really mapped it out and I stuck pretty well to what I thought I should do. I really challenged myself today. I don't know how the other scores look. I'm sure there are going to be some pretty low ones because of the greens being soft."

Britons Westwood and Rock set the earlier pace, the world No 10 looking solid during a round that included six birdies.

Rock has good memories of the tournament, after finishing 14th and 17th in the last two years, and he is hoping to improve even further this time on what he described as "one of the best courses in the world".

"I don't really know why that is. But I think it's just early in the calendar, and you're keen to get off to a decent start," he said.

"I think the course here is something that I really like, so I'm always a little more excited than normal to come and play."

Yorkshire's four-strong contingent all made solid but unspectacular starts. York's Simon Dyson, Richard Finch, of Hull, and Iain Pyman (Leeds) shot one-under-par 71 with Rotherham's Danny Willett a shot further back.