Britain's  Paula Radcliffe won the Chicago Marathon yesterday and shattered the world record with a time of two hours, 17 minutes and 18 seconds.

In only her second serious attempt at the distance, Radcliffe bettered the previous best of 2:18:47, set by Kenyan Catherine Ndereba in winning in Chicago last year.

Khalid Khannouchi won the men's race in 2:05:56. The Moroccan-born American was unable to improve on his own world best time of 2:05:38, set on April 14th in London.

Radcliffe also won in London in her debut at the distance, running 2:18:56 for what was then the second-fastest women's marathon ever. With their performances in London and Chicago, Khannouchi and Radcliffe have the two fastest men's and women's races, respectively, ever in a single calendar year.

Khannouchi now has run three of the top four fastest marathons of all time, while Radcliffe owns two of the three fastest women's times.

It was 28-year-old Radcliffe who stole the show as she seized the lead from the start and came through the half-way point in 1:09:01, running with the strength and determination that has become her trademark.

"The wind is tough," said Radcliffe, whose second-half split was faster than her first and who seemed untroubled by the headwind of the final two miles.

"I felt good through the first half, and then I just wanted to run through the second half. I was kicking hard at the end. I felt strong at the finish.

"I intentionally held back in the first half of the race and then stepped it up in the second."

Radcliffe admitted she nearly had to stop for a call of nature.

"I needed the loo at the 22km mark and thought I would have to stop," said the reigning world cross country, Commonwealth 5,000 metres and European 10,000m champion.

She paid special tribute to her husband, Gary Lough, though he played down his role.

"He's been great because he had to put up with all the stress this week, and plus he was ill, so he had to stay away from me," she said.

Radcliffe also revelled in the fact it was in the United States 10 years ago she signalled her ability as an athlete when she won the world junior half-marathon title.

"America's been good for me and this has been a simply dream-like experience today," she said.

"However now I am going to throw away the trainers and take a good long holiday."

Ndereba, who was going for her third Chicago victory in a row, was second in 2:19:26, and Japan's Yoko Shibui was third in 2:21.22.