Devon's Jonathan Tiernan-Locke seized the overall lead of the Tour of Britain with an aggressive ride on the sixth stage in Wales.
Leopold Koenig (Team NetApp) claimed victory on the 189.8-kilometre route from Welshpool to Caerphilly and Tiernan-Locke (Endura Racing) finished second to assume the race leader's gold jersey with two days of racing remaining.
The 27-year-old from Plymouth, who is rumoured to be joining Team Sky in 2013 and was named in the British team for next week's road World Championships, began the day in sixth place, 24 seconds behind Leigh Howard (Orica-GreenEdge).
But now Tiernan-Locke, who received a six-second time bonus for placing second, has a 13-second lead over Howard ahead of the seventh stage from Barnstaple to Dartmouth.
The eight-stage race concludes with Sunday's Surrey route from Reigate to Guildford.
Tour de France winner Bradley Wiggins was a non-starter in Welshpool after an eventful fifth stage to Stoke-on-Trent for Team Sky, which saw Mark Cavendish relinquish the race lead to Howard.
Six riders formed the breakaway on a day which saw the riders go over the Brecon Beacons.
Their advantage was cut to less than a minute with two ascents of Caerphilly Mountain to come before the finish in front of Caerphilly Castle.
On the first climb of Caerphilly Mountain, Tiernan-Locke attacked from the peloton as the escape group splintered in front of him.
Only escapee Graham Briggs (Raleigh-GAC) could stay with him, but Koenig (Team NetApp) bridged the gap before Briggs fell back on the lower slopes of the second ascent of the finishing climb.
British academy rider Josh Edmondson was alone in pursuit but was swept up by a larger chase group, led by Ivan Basso (Liquigas-Cannondale), in the closing kilometres.
Koenig belatedly helped to share the workload with Tiernan-Locke in the closing moments before sprinting away to victory by one second.
Nathan Haas (Garmin-Sharp) won the sprint for third to move to third place overall, 18 seconds behind.
Luke Rowe (Team Sky) was fifth on the stage.Koenig began the day more than five minutes behind and was not a threat overall, so Tiernan-Locke was content not to battle for the stage win.
"That was always going to be the decisive day today, such a sharp climb twice," Tiernan-Locke told ITV4.
"It was a tough one. I'm relieved to get across the line with a gap still.
"A stage win would've been nice, but I had company and I got a bit of work shared.
"I was happy to let the stage win slip by. The overall is the main goal this year.
"We're going to try and not let it (the gold jersey) go now."
Tiernan-Locke, who believes Haas is now his biggest rival, will aim to enhance his advantage tomorrow on roads he knows well.
He added: "It's pretty slim. We'll need some more (time) and attack the finish again.
"It's going to be great. I'm counting on a lot of support there. I'm sure it's going to be amazing."