Ben Ainslie's charge for Olympic sailing gold faltered again as Finn leader Jonas Hogh-Christensen palmed off the reigning champion for a sixth successive race.
The three-time gold medallist came into London 2012 as overriding favourite to top the podium, but has yet to overcome the Dane on home waters.
Hogh-Christensen got his third bullet - a victory - of the regatta in race five, and then held off a late surge from Ainslie to finish second ahead of him in the day's final Finn race.
With the home favourite finishing fourth in the first race, the Danish 2009 world champion is now 10 points better off in the overall standings heading into Wednesday's rest day. The Star class also have Wednesday off, which British pair Iain Percy and Andrew Simpson will be able to enjoy after pulling four points clear at the top of the fleet.
The defending gold medallists won race five at a canter, 50 seconds ahead of rivals Brazil. Robert Scheidt and Bruno Prada managed to win the final race of the day though, as Percy and Simpson snuck over the line in second ahead of Sweden.
British team-mate Ali Young also enjoyed a successful day, securing two second-place finishes in the Laser Radial class, both behind Ireland's Annalise Murphy - winner of all four races so far.
Stevie Morrison and Ben Rhodes started well in the 49er class, having posted two 12th-place finishes on Monday. The British pair finished the day's first race third and were well placed in the second, only to capsize and come home 18th.
Australia's Nathan Outteridge and Iain Jensen continued to lead the 49er class after finishing second to New Zealand in the first race and fourth in the second, having capsized when leading.
The RS:X classes got under way and Nick Dempsey got off to solid start in the men's division, hauling himself up the fleet in both races to post a fifth and seventh. The Norwich-born windsurfer stands fourth in the overall standings, with Holland's Dorian van Rijsselberge leading the way after winning both races.
In the corresponding women's event, Beijing bronze medallist Bryony Shaw ended her first day at London 2012 with a seventh and a sixth.