Robertson won the world mixed doubles title with Gail Emms in 2006

Nathan Robertson's Olympic preparations will be on hold for six weeks, after undergoing surgery on his ankle.

It was hoped that the 30-year-old, who won Olympic mixed doubles silver with Gail Emms four years ago, would not need an operation until after Beijing.

But England head coach Ian Wright said: "There are foreign bodies inside the ankle joint and it is prudent to clear it up and give Nathan piece of mind.

"It's unfortunate the recovery cuts into our 12-week Olympic preparations."

However, Robertson should be fully fit for the tournament at the Games which begins on 9 August.

Robertson and Emms won the world mixed doubles title in 2006, but have struggled to match that form since and lost at the semi-final stage of both the All England Championships in March and the Europeans last month.

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Wright added: "Nathan has been under-prepared for every tournament for the last six months."

The qualifying period for the Olympic Games ended on Thursday and the Badminton World Federation ranking list will be used to determine who is invited to play in Beijing.

However the GB team will not be announced until 22 May.

Robertson and Emms are ranked sixth in the world and look set to feature in Beijing alongside current European mixed doubles champions Anthony Clark and Donna Kellogg, who are ranked eighth.

In the singles, Tracey Hallam, who is 14th in the women's world rankings, and Andrew Smith, who is 31st in the men's rankings, are also looking likely to be in the squad.