Mark Hunter and Zac Purchase put a troubled season behind them to open the defence of their Olympic title by winning their rowing lightweight double scull heat in commanding fashion.
Hunter and Purchase felt at rock bottom after successive sixth place finishes in the World Cup series - but they have a reputation for performing best on the biggest stages.
The world champions led chief rivals New Zealand from the start and held off a late Kiwi charge to win by half a length, in six minutes 36 seconds.
Both crews progress into the semi-finals but to have won in such fashion will have been a confidence boost for the British crew - and may serve as a statement of intent to the rest of the field.
Sophie Hosking and Katherine Copeland were similarly successful in the women's lightweight double, dominating their heat to win by clear water and cruise into the semi-finals.
World championship bronze medallists last year, Hosking and Copeland edged ahead of New Zealand at the half-way mark and then pulled clear in a supreme exhibition of sculling.
New Zealand set the world's fastest time in Lucerne earlier this year and won gold at the Munich World Cup regatta but they could not live with the British crew.
Hosking and Copeland were seven seconds faster than world champions Greece, who won the second heat and 19 seconds up on third heat-winners China.