Great Britain's women's pair and men's eight battled to silver medals at rowing's World Championships in Bled, Slovenia, on Thursday.
Helen Glover and Heather Stanning were defeated by New Zealand for the women's pair world title in a thrilling final.
Britain's men's eight had to settle for second behind Germany's dominant crew.
Peter Chambers and Kieren Emery won Britain's first title of the 2011 Worlds in the men's lightweight pair, which is not an Olympic event.
Glover and Stanning, who have dominated this year's World Cups in the women's pair, looked likely to hold on for a memorable victory over New Zealand's defending champions Juliette Haigh and Rebecca Scown.
However, they surrendered their slender lead in the final metres, recording a time of six minutes 58.24 seconds behind their rivals' 6:58.16 - a gap of just 0.08 seconds.
"I'm sure it was a better race to watch than to be in but it was a great race by the Kiwis," Glover told BBC Sport.
"It's still a great result and it gives us somewhere to go - we've got a year to get there."
Stanning said: "It was a fast race considering how rough the water was and, unfortunately for us, they were outstanding today."
The men's eight final developed into a scrap for silver and bronze as an impressive German crew, unbeaten in three years, strode to another world title.
Britain sat back in fourth place for the first 500m of the race but hauled themselves up into silver-medal position to replicate last year's result, ahead of Canada.
"The Germans are very classy," said 39-year-old Greg Searle, a gold medallist at the Barcelona 1992 Olympics who returned to the British team from retirement in 2010.
"We will be very motivated for 11 months to the day."
BBC summariser Sir Steve Redgrave, five times an Olympic rowing champion, said: "I am a little bit disappointed, following such a good season for the women's pair, that they took the silver.
"In saying that, it has given everyone confidence that next year they can go on to take Olympic gold.
"The eight taking the silver is what I expected to happen, with the Germans winning, but I have a slight worry that the chasing pack is now closing in on the British crew."
Youthful duo Chambers and Emery initially had to contend with pressure from New Zealand in the final of the men's lightweight pairs, which is not an Olympic class and hence will not feature at London 2012.
But their race came down to a battle against the German boat, with the British maintaining the upper hand throughout.
"It feels pretty awesome. We worked really hard beforehand, and came here feeling really strong and really up for it," said Emery.
Chambers added: "We stayed in the race for the first kilometre and from there we went as hard as we could go."
Earlier in the day, Britain's women's quadruple sculls crew qualified their boat for London 2012 by winning their B final.
Mel Wilson, Beth Rodford, Annabel Vernon and Debbie Flood missed out on a place in the A final during Wednesday's racing, despite coming to Bled as the reigning champions.
But victory in the B final ahead of Poland and Italy ensured the quartet recovered to earn Britain's boat a place at next year's Olympic Games.
There was joy for the Paralympic-class mixed adaptive double duo of Nick Beighton and Sam Scowen, as they became the first boat to confirm their place at the London Games.
The pair finished second behind Australia in their repechage but secured a top-eight place.
Beighton said: "It's a big relief to qualify for the Games. That has been our target here all along."