The 33-year-old breezed through the first game but then had to survive an onslaught from Xie, whose boyfriend Lin Dan will play in the men's singles final today.

Xie looked devastated to only win silver. Indonesia's Maria Kristin Yulianti took the bronze.

"I think it was tenacity derived from being 33-years-old at the Beijing Olympics in the final that allowed me to win in the end," Zhang told a news conference.

Zhang looked every bit as fit and fast as her 27-year-old opponent, with a heavily strapped right knee the only sign of the injuries she has been plagued with since the 2004 Games.

"It's normal for either of us to win or lose this game," said a despondent Xie. "I think today I wasn't as fast as Zhang Ning."

A subdued crowd took a while to get into the match but warmed to the occasion as Zhang pushed the world number one around the court to take the first game 21-12.

Xie found her rhythm in the second game, mixing it up with bewildering flurries of spiralling lobs and punishing drop shots to take it 21-10.

The writing looked to be on the wall for Zhang, who by now was flicking sweat to the sidelines and breathing heavily.

She took an early lead in the deciding game but seemed to tire as it went on and allowed Xie to tie it up at 15-15.

However, the Athens gold medalist somehow conjured up a burst of energy to pick up the pace and turn the tables on Xie.

Zhang clinched the match 21-18, jumping for joy before sinking to her knees, burying her head in her hands and wiping away the tears.