Grainger, 36, and Anna Watkins, 29, finally triumphed in the women’s Double Sculls, clocking six minutes 55.82 seconds in blustery conditions.
The duo took an early lead ahead of Australia’s Brooke Pratley and Kim Crow, extending it to half-a-length by 500m. But at the halfway mark the Brits upped their stroke rate in a final push for the finish line that thrilled spectators.
Their victory by a length confirmed Grainger, who has been rowing since 1993, as the most successful British female of all time in the sport – and eased the pain of a knife-edge defeat to host nation China in 2008, after which she had considered retirement.
It was a hugely emotional win for both women, and immediately after the race Sir Steve Redgrave embraced Grainger . If ever there was a success story that illustrated the benefits of never giving up, this was it.
She said: ‘Worth the wait. Steve promised me they’d be tears of joy this time, which there are. I feel this medal of all of them is the people's medal. I feel so many people have been behind me and supported me and wanted this for me as much as I have.’
Grainger had racked up three Olympic silver medals since a friend at Edinburgh University dragged her along to a novice meet.
Enter Anna Watkins, who rowed at Cambridge University and was talent-spotted spotted by GB Rowing’s World Class Start scheme. Since the two joined forces in 2010 they have been unbeaten in 23 races, claiming two World Championship titles, bringing the Scot’s total to six world gold medals.
It’s a natural partnership, and observers of the sport have noted their powerful, instinctive sprinting, confidence and graceful, matching strokes.
The unstoppable duo helped Team GB to its best ever medal haul on Dorney Lake, with four golds and nine medals in total.
But winning gold was clearly the achievement of very personal ambition for Grainger. After taking the top spot on the podium she said: ‘It’s everything you hope it could be. On the podium we both knew how special it was.
‘It’s the fulfillment of a lot of blood sweat and tears but it doesn't all sink in. Any Olympic medal is a phenomenal achievement but having had three in the past I wanted a gold one to complete the collection.’
It’s unclear whether the partnership will last until Rio in 2016 – but even if it doesn’t, Grainger will be able to retire happy in the knowledge that she reached the summit of her sport.