Alistair Brownlee powered away in the final third to win the Hyde Park triathlon and meet GB's selection criteria for the 2012 London Olympics.
The 23-year-old from Yorkshire led with three others at the end of the cycle but ran clear to finish 25 seconds ahead of Russian Alexander Bryukhankov.
Alistair's brother Jonathan also met the 2012 criteria by finishing third.
Hyde Park forms one of triathlon's seven-leg World Championship Series, with the finale in Beijing next month.
Following his earlier wins in Madrid and Kitzbuhel, Alistair Brownlee has now won three of five legs so far this season, as well as the European title in Spain.
However, Sunday's victory on home soil will be of particular satisfaction to the elder Brownlee brother as it comes on the track that will be used for next year's Olympics, where the Dewsbury-born man will be considered one of the favourites for gold.
Prior to the race, Brownlee had claimed the course did not suit his style, suggesting a less flat terrain and tougher ride and run would fit him better, but his approach was faultless despite persistent heavy rain throughout the second half.
He reached the transition between the swim and cycle in the top 10 before quickly establishing a lead in the middle third along with Bryukhankov, New Zealander James Elvery and Spaniard Ivan Rana.
"To be honest I couldn't believe I got away on the bike," said Brownlee. "I was worried I would be attacked on the bike."
The latter two dropped away following the final transition, in which Brownlee came into his own to win by a huge margin ahead of the gutsy Bryukhankov.
Last year, Brownlee collapsed from exhaustion in the final few metres of the race, allowing Spaniard Javier Gomez to overtake him for gold, but this time he was able to lap up the cheers of the home crowd while walking over the line.
There he was able to wait to congratulate younger brother Jonathan, who had pulled away from world champion Gomez in the closing stages to claim bronze.
William Clarke finished 14th, with fellow Brits Adam Bowden 32nd and Stuart Hayes 46th.
The World Championship Series next moves to Lausanne, Switzerland, on 20-21 August before the series' grand final in Beijing on 10-11 September.