Overnight leader Tjaart van der Walt threw away a three-shot mid-round advantage to concede a share of top spot to England's Robert Dinwiddie on day two at the St Omer Open.

London-based Dinwiddie, a morning starter, had set the clubhouse lead on four under after a blemish-free 66, one of the best rounds of the day in improving conditions in northern France.

"Considering I didn't think I would be teeing it up, after taking a bad step on Tuesday morning and damaging a bad disc in my back, it was great," the 30-year-old told europeantour.com.

"I couldn't hit a ball on Wednesday so I honestly thought I had no chance but I just iced it and took a lot of anti-inflammatories and recovered so it was great.

"I played really steady so I'm happy. The weather was much easier today and I played just as well yesterday but the weather just helped.

"I know the course very well and I have a lot of good feelings around here."

But before Dinwiddie had the chance to sit back and reflect on his round Van der Walt, teeing off after lunch, was well into his stride as he birdied the 396-yard first and picked up two further shots at the fourth and fifth, also short par fours.

However, things started to go awry for the South African when he bogeyed the ninth and although he got that shot back at the next three bogeys in his last seven holes dropped him back into a tie for first place after a level-par round of 71.

Stafford's Simon Wakefield moved to within one of the lead with a 68 and he was joined by compatriot Chris Hanson (68) and Frenchman Victor Riu (71).

Berkshire's Seve Benson leapt 59 places into a share of sixth on two under after an equal-best of the day 65, which included eight