Great Britain's men's eight beat Olympic champions Germany in the final of the Grand Challenge Cup at Henley Royal Regatta.
Rowing as Leander and Molesey Boat Club, the world champions won by two-and-three-quarter lengths.
The result gave Britain the ideal preparation for the next World Cup event in Lucerne later this month.
Team member Alex Gregory said: "It makes us really positive and confident that we can perform when it matters."
Germany had beaten GB to the European title in Poznan in May before the boat, coxed by Henry Fieldman, gained its revenge in the last World Cup leg in Varese.
Those races had been close but after holding the Germans' strong start at Henley, the GB boat pulled clear to win by an emphatic margin.
Gregory, Olympic 2012 gold medallist in the men's four and 2013 World Champion in the eight, added: "We thought it was going to be a battle right to the line but to put that distance in is a real step forward for us. We are in a great position now."
Canada beat GB to win the Remenham Challenge Cup for elite women's eights.
The British boat was in contention for the early part of the race before fading in the second half.
Twenty head-to-head finals, from schools up to international crews, took place on the final day of the regatta.
Regatta chairman Sir Steve Redgrave said: "What a fantastic event we have had. New records and great racing and that's what sport is all about."