Henrik Stenson produced a storming finish to claim a one-shot lead at the halfway stage of the Nedbank Golf Challenge.

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Shortly after play resumed following a two-hour delay due to a thunderstorm, Stenson trailed playing partner and local favourite Jaco van Zyl by three shots with seven holes to play.

However, the world No7, who rated his chances of simply playing in the event at five per cent after spending three days in bed with the flu, rolled in a hat-trick of birdies from the 13th and picked up another shot on the 17th to add a 67 to his opening 66.

At 11-under par Stenson was one shot ahead of Van Zyl, who had started his round birdie, eagle before eventually settling for a 68, with American Robert Streb another shot back following a 66, the lowest round of the day.

“I’m surprised. On Wednesday afternoon, I didn’t think I would be able to tee it up,” Stenson admitted. “I thought I was done and dusted, so to be leading after two days, it’s a turnaround to say the least. But the saying is ‘Beware of the injured or sick golfer’ and I guess that’s true.

“I just tried to stay patient and get round and I’ve done that pretty well so far. I’m getting over the virus, but I was more fatigued this morning than I was yesterday just because of playing yesterday. It takes a lot out of you playing in 35 to 40 degrees when you’re not physically well.

“I’m heading in the right direction, but I’m not getting a chance to rest up much. Tomorrow, I’ll probably have very heavy legs again, but being in the hunt for a tournament should get me going.”

Stenson had followed three birdies in the first five holes with a hattrick of bogeys from the sixth and admitted that the thunderstorm delay came at the right time.

The 39-year-old, who was on the 10th hole at the time, said: “I didn’t do too much wrong but managed to string three bogeys in a row, so at that time it was probably good to have a break and it really cooled down afterwards for the back nine.

“I got the putter going – that was hot at least – and made a couple of nice birdie putts. All in all a very good back nine turned an average round into a good one.”

Meanwhile, Danny Willett’s title defence was hampered by a back injury. He began the day just a shot off the lead but ended it nine adrift after a round of 75.

The 28-year-old was in obvious distress from the recurrence of a long-standing back injury and after playing the first five holes in four over, lay down on the sixth fairway and performed stretching exercises before receiving treatment from the Tour physio on the ninth tee.