Double Olympic medallist Nick Willis is confident he can rediscover his best form in time for next year's Commonwealth Games following under-the-radar post-Rio surgery.

Willis finished a battling eighth in the 1500m world championship final in London, but was satisfied with his effort given an injury-ridden start to the season.

"I haven't told anyone publicly but six weeks after the Rio Olympics I had surgery on a sports hernia double release on my adductors," he said yesterday.

"I spun it that I needed to take three months off for a break as I really didn't want meet directors to know that I was going under the knife and I might miss out on appearance fees the following year.

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"That probably played a role in the injuries after that but now I'm fully healthy and still improving," he said.

Willis's world championship build-up was restricted by persistent shin splints from the end of March, with his efforts to train through the painful injury less than successful.

"It was only in June that I got back to regular jogging and I didn't start work outs until the last weekend in June."

Willis, who won 1500m bronze in Rio last August and silver in Beijing eight years earlier, now shifts his focus to next year's Gold Coast Commonwealth Games, and while it's not definite, seems likely to contest both the 1500m and 5000m, as he did in Glasgow 2014 where he took bronze in the shorter race, and finished 10th over 5000m.

Quentin Rew secured a place in the New Zealand record books with an expertly-timed performance in the 50km walk. Rio Olympian Rew surged home 12th, clocking a national record 3h 46min 29s. It eclipsed Craig Barrett's 16-year-old previous national mark by 1min 34s.

Rew was 29th after the first 5km but spent the rest of the race making up places, improving six spots over the last 5km in hot conditions.