Radcliffe was two minutes quicker at halfway than in London

In the men's race, world record holder Khalid Khannouchi won in Chicago for a fourth time.

But the Moroccan-born athlete, who now runs for the United States, narrowly missed his own world record set in last year's event.

Radcliffe's victory added to a bulging portfolio of achievements this year.

She has already retained her world cross country title, won her debut marathon in London and took Commonwealth 5,000m and European 10,000m gold.

Her winning time in London was two hours, 18 minutes and 55 seconds - the fastest ever by a woman in a women-only field.

But she obliterated that on the banks of Lake Michigan, running the second half of the race a minute quicker than the first.

World record pace

Sporting a sky blue hat and white gloves in the sunny but cool conditions, Radcliffe settled among a group of elite men's runners as she led the women's race from the outset.

After half an hour, it was clear Radliffe was operating at a pace faster than any woman had run before, the forecast rain failing to materialise.

And as she went through 10 miles in 52 minutes and 37 seconds, she remained around a minute inside world record pace.

But there were three other women within close proximity, with world record holder Ndereba a mere 10 metres behind her.

Japanese duo Yoko Shibui and Masako Chiba were also in touch along with American Deena Drossin.

But Ndereba, who set the old record in Chicago last year as she recorded her second consecutive victory, was the only one to stay with Radcliffe's relentless onslaught.

The Briton reached the halfway point in 69 minutes and five seconds - two minutes faster than her debut marathon in London.

Khannouchi's fourth victory

At 19 miles she ran her second quickest mile of the race, five minutes and five seconds, to move 22 seconds clear of Ndereba.

And she continued to stretch away to finish two minutes and nine seconds ahead of the Kenyan, second in 2:19:26, with Shibui third nearly two minutes further back in 2:21:22

Khannouchi, Chicago winner in 1997, 1999 and 2000, lived up to his favourite's billing after his world record in London six months ago.

He was happy to remain slightly off the pace on the early stages, but joined the leading group around the halfway mark.

Kenya's Paul Tergat and Moroccan Abdelkader El Mouaziz did their share of the front-running as the leading group went through 13 miles in 62 minutes and 30 seconds, around 40 seconds inside Khannouchi's world record pace.

Japan's Toshinari Takaoka made a surprise break with less than 10 miles to go, at one point stretching ahead of the pack by 60m.

But Khannouchi hauled him in with less than two miles to go and stretched away to win in two hours, five minutes and 56 seconds, 14 seconds outside his own world record.

Kenyan Daniel Njenga was given second place ahead of Takaoka, who both finished in the same time of 2:06:16, with Tergat two seconds further back in fourth.