Great Britain's Non Stanford was crowned world triathlon champion after winning the Grand Final in Hyde Park.
The 24-year-old dominated the 10 kilometre run despite having to take a 15-second penalty.
Stanford's British team-mate Jodie Stimpson finished fourth in the race, which earned her the silver medal in the overall world series.
It was a dramatic race, with the two leading athletes in the standings, American Gwen Jorgensen and Germany's Anne Haug, both dropping out of contention.
Haug never recovered from a terrible swim while Jorgensen crashed on the bike.
Stanford was the world under-23 champion last year and becomes the second athlete after her compatriot Alistair Brownlee to win the two titles in successive seasons.
The Welshwoman's achievement is all the more impressive given she broke her arm in a crash on the bike in Hamburg in July but recovered to finish second in Stockholm just five weeks later.
Stanford succeeds fellow Welshwoman Helen Jenkins, who was world champion in 2008 and 2011 but has missed this season through injury.
It was cold and grey but dry as the field dived into the Serpentine for the start of the 1.5 kilometre swim.
Stimpson and Stanford stayed with the leading pack but it was obvious after the first lap that Haug was in big trouble.
The German was almost a minute behind and swimming on her own, and by the time she collected her bike the deficit was more than two minutes.
Stanford had trouble putting her cycling helmet on and in her rush to get away from transition she failed to put her wetsuit in the box, earning a 15-second penalty.
A sizeable lead group soon formed on the bike, including Stanford, Stimpson and Jorgensen, but the American's race was all but ended when she came down heavily at a corner on the second lap.
She remounted but never looked comfortable and pulled out soon after.
Haug, meanwhile, was making no impression on the leaders, which put the two British athletes in a very strong position.
Stanford knew she would have to really go for it on the run, and she shot out of transition and straight into the lead.
Stimpson had trouble putting her left shoe on, which dropped her down the field a bit.
By the end of lap two, Stanford had her 15-second lead over USA's Sarah Groff, with Stimpson in a small group a further 15 seconds back.
Stanford took her penalty early on the final lap - as Jonny Brownlee did at the Olympics last year - but emerged still well ahead of Groff and was never troubled, grabbing a Welsh flag as she raced down the finishing straight.
Stimpson finished strongly to take fourth in the race, which was more than enough for silver overall, behind Ireland's Aileen Reid and Emma Moffatt of Australia, with Groff dropping out of contention.