The duo, unbeaten together since joining forces in 2010, powered out to a 500-metre lead that they never relinquished – claiming a new Olympic record of 6:44.33 minutes.
The men’s four of Pete Reed, Alex Gregory, Andrew Triggs-Hodge and Tom James started their Olympic defence in style with a powerful opening performance.
Great Britain followed main rival Australia’s impressive first heat display with an equally comfortable row of 5:50.27 to coast into Thursday’s semi-finals.
The women’s quad scull of Fran Houghton, Debbie Flood, Beth Rodford and Melanie Wilson produced an excellent display to qualify for the final on Wednesday.
In the repechage, Team GB trailed at half way but capitalised on a problem with the New Zealand boat to seize third place in a time of 6:21.65.
Greg Searle’s hopes of a second Olympic gold medal, 20 years after his first, are still alive after the men’s eight dominated their repechage to win in a time of 5:26.85.
Searle, who won gold alongside his brother Jonny at Barcelona 1992, helped Team GB start strongly and they controlled the race to beat defending champions Canada into second place.