Great Britain won the Olympic title in the men's coxless four for the fourth successive Games, edging out Australia in a thrilling race at Eton Dorney.
Pete Reed, Andy Triggs Hodge, Tom James and Alex Gregory clocked six minutes 3.97 seconds, with USA taking bronze.
It was British rowing's third gold medal of the regatta to match their record haul in London 1908.
"It was probably the best they have rowed. They were smooth, strong and powerful. It was fantastic rowing from the guys."
And it took the team's medal total to seven to make London 2012 their most successful Olympics in the modern era.
Sophie Hosking and Katherine Copeland
won gold in the lightweight women's double sculls, and
Mark Hunter and Zac Purchase won silver in the lightweight men's double sculls
to boost the medal total to nine.
Only twice has a crew managed to win gold in the men's four on four successive occasions - Britain between 1908 and 1932 and East Germany between 1968 and 1980.
Reed, Triggs Hodge and James won their second Olympic gold medal after their success in Beijing, but it was the first of any colour for Gregory in a boat.
The boat was made famous by Sir Steve Redgrave, Sir Matthew Pinsent and James Cracknell, who have nine gold medals between them.
2012 rowing medal table
Great Britain - 9 (four gold, two silver, three bronze)
New Zealand - 5 (three gold, two bronze)
Germany - 3 (two gold, one silver)
Denmark - 3 (one gold, one silver, one bronze)
Czech Republic - 2 (one gold, one silver)
Triggs Hodge described the race as the crew's "masterpiece".
He told BBC Sport: "It took four years to make that. These guys are absolutely phenomenal. It was just impeccable rowing.
"I'm the happiest man in the world."
James said: "I can't describe what this atmosphere is like. It's beyond words, it's epic, it's magic, it's emotional. The crowd is phenomenal. I'm so excited to be here and so proud."
Reed said he could not believe he was a double Olympic champion and added: "I can't believe it. The hours we do, the hours, the pain. It's all worth it at the end."
The men's coxless four receive their gold medals
It was an impressive performance from a crew who were on the back foot after men's head coach Jurgen Grobler gambled by shuffling them around just months before the Olympic regatta.
They secured victory in the first two World Cups but lost the semi-final and final to rivals Australia in the last.
They upped their game at Eton Dorney, taking a confidence-boosting victory over Australia with a late surge in the semi-finals.
Roared on by a capacity crowd in the final, they blasted out of the blocks to take a psychological lead after 500m.
The Australians, who last won gold in the event at Atlanta, refused to give in and stayed within a third of a length with 500m to go.
But Triggs Hodge gave the call to push and the British stormed away as they entered the stadium section of the course to win by a length and extend the nation's golden dynasty in the event to 16 years.