Norway's Eirik Veras Larsen won gold today in the kayak sprint as Tim Brabants, defending his Olympic crown, finished eighth.
World champion Adam van Koeverden finished second to claim silver, while Max Hoff from Germany won the bronze.
Brabants, who came in to the Games struggling for full fitness following a serious tendon injury, could never contest the lead at Eton Dorney.
Drawn in lane one nearest the grandstand, the 35-year-old had the support of the home crowd but fell well behind Canada's Van Koeverden as he surged in to an early lead.
But with 250 metres to go in the individual 1000 metre kayak sprint, Larsen edged in to first place to claim gold.
Speaking to reporters afterwards, Brabants said he felt good in his warm up but was disappointed with the result.
He said: "Unfortunately today the other guys were better. Everybody in that final has been in a final this year, at the world cup and the Europeans, except me.
"To be in the final was my main aim and then to try and make that podium again. I felt like I could. In the warm up I felt strong but unfortunately I felt like I was never in the race for some reason.
"The conditions weren't bad. I am not making excuses at all. I would rather not have had lane one but it didn't make a difference on the day.
"The right guys won and they showed their class, they showed their form. My main problem is letting down the home crowd. I wanted to add to the medal tally for Team GB like all the other athletes and especially like the returning gold medallists from Beijing who have done so."
"I am really looking forward to seeing our 200 metre boys racing - maybe they will pick up when I missed out."
Asked whether he intended to continue, the accident and emergency doctor said he would return to his day job, probably at Nottingham's Queen's Medical Centre, in the next few weeks but seemed to rule out competing in Rio in four years.
He added: "I don't want to give up just yet. We work on four year cycles. This is the end of one cycle and so in a few weeks time we will reassess where we are. I love the sport. I love being in this environment, so I certainly don't want to stop just yet.
"Another four years is a tough one. I will be 39 in Rio so I think it is unlikely and unrealistic but I don't want to give up just yet - there are all sorts of other competitions we can compete in."
He added: "I am happy for the guys who have won. I know they are good athletes and I know they are clean athletes, which is the key thing for me - knowing that the top guys on the podium are clean. I am happy for them but I am disappointed for me.
"There always are (athletes who dope) unfortunately but time will tell but there are guys who I have raced throughout the last 12 years who disappear for two years on a ban and then they come back and they are racing again. It's part of our sport unfortunately and all we can do as British athletes is promote drug free sport.
"As I say, I am pleased for the guys on top of the podium because I know they are good athletes and worthy champions."
In the women's K4 500m, Jess Walker, Angela Hannah, Rachel Cawthorn and Louisa Sawers finished fifth, behind Hungary, who won gold.
Germany's Sebastian Brendel won gold in the men's 1000m canoe sprint, while David Cal Figueroa from Portugal from Spain finished in second. Canada's Mark Oldershaw claimed the bronze.
In the men's kayak double, Hungary's Rudolf Dombi and Roland Kokeny won gold, Portugal's Fernando Pimenta and Emanuel Silva took the silver and Martin Hollstein and Andreas Ihle from Germany won bronze.
Speaking after the men's K1 1,000m, silver medallist van Koeverden said he had trained with Larsen in the region of 1,000 times over the last 14 years.
He said: "We are 50-50 for wins in those sessions. In those sessions we get off the water and we have said to each other many, many times, 'I don't think anybody in the world could have done what we did today'.
"We are not being cocky, or arrogant or boastful. Today was no exception, we flipped a coin and if it comes out the wrong side you have to deal with it.
"I have said it before that I don't like stacking up my 1,000m silvers on my dresser at home but if I have to lose to somebody then he is a classy guy and I respect him so much."
Germany claimed the silver in the women's K4, while Belarus won bronze.
Speaking after the race, Sawers said she was not affected by the windy conditions at Eton Dorney.
The 24-year-old, from Walton-on-Thames, Surrey, said: "We saw the Belarusians come through but we just stuck to our race plan. Our finish was just not fast enough. I was quite excited about the K4 because we have an international ranking.
"The training went well but the standard was pretty high out there. I think we performed as best we could."
Walker, who competed in Beijing, said she hoped to improve over the next four years for the Olympics in Rio.
The 22-year-old from London said: "One day we will get there one day. The last four years has been about this Olympics. I will be there in Rio. After you've done your first Olympics, you then go on and medal at your next one but I think this is the one before I medal in my K4."
Walker now competes in the women's K1 200 metres. She added: "Hopefully I will have a better mentality when I get to that final."
Angela Hannah, 26, from Loughborough, Leicestershire, who played hockey for Zimbabwe as a youngster before she was spotted for Team GB's canoeing team, said she planned to spend the rest of the week watching other events.
She said: "Five years ago the whole idea was for me to get into the boat and learn how to paddle and get here. Even, a year-and-a-half ago I didn't think I could get that far. But to call yourself an Olympian is amazing. It's such a privilege."
Cawthorn, 23, from Guildford, Surrey, said: "I am absolutely happy I had the K4 the first day because the first time we went out in front of that crowd is what like 'whoa'. We have never raced in front of anything like that before so that when it came to the K1 it felt a bit more like home.
"I have one more chance to go out there and put down my best race and see what happens. I am really looking forward to go out there again and do my best race."