Chrissie Wellington set a new world record for a sanctioned Ironman event as she won Ironman Arizona on Sunday.
The 33-year-old from Norfolk returned to action after withdrawing from her third defence of September's World championship in Hawaii.
Wellington completed the 140-mile course in a record eight hours, 36 minutes and 13 seconds.
Britain's Leanda Cave finished third, and Wellington's boyfriend Tom Lowe was third in the men's race.
Wellington told BBC Radio Norfolk she was delighted to end a frustrating season on a high.
"Missing Kona was a huge disappointment, but I knew that if I got my health back that I was fit and I knew that I had done all the hard work to put in a great performance.
"That's why I was so keen to race, just to do justice to all of my hard work," she said.
"I didn't expect to break the World record, but I'm so incredibly proud, it was an awesome race with an incredible support, and I thrive on the energy from the crowd," she added.
Lowe, on his Ironman debut, was one of just seven men to avoid being beaten by Wellington, who ran at astonishing pace to complete the final stage, a full marathon run, in 2:52:55.
Wellington trailed Cave by 43 seconds at the end of the 2.4-mile swim, but took the lead and maintained it at steady pace on the 112-mile bike leg.
Her time was 17 minutes short of the overall long-distance world record she set at Germany's Challenge Roth in July.
Wellington, who was named an MBE in the Queen's birthday honours list this year, withdrew from September's World Championship after contracting pneumonia, strep throat and West Nile virus, missing out on a fourth consecutive title.
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