Lundy donned a British team kit and rowed 1,000 metres of the London Games course on Dorney Lake, as she had pledged to do if Britain won more medals than Australia during the Olympics.
Britain took 65 medals, including 29 gold, while Australia collected 35 medals with 7 gold.
Crowds cheered Lundy, a former rower, as she took to the water in a single scull to carry out her forfeit.
"It's a fantastic opportunity. I'm very grateful to the minister for suggesting this should be my ritual humiliation," Lundy said after completing the task.
Had Britain fallen short, sports minister Hugh Robertson had promised to wear an Australian field hockey uniform and dribble a ball around Australia House, the country's official government residence in London.
"I'd rather not use the word humiliation. There was a bet and a forfeit and we both wanted to pick a sport we were familiar with," said Robertson, who was on hand to watch Lundy.