Boardman dominated the 128-mile stage from Edinburgh to Newcastle. Going clear of the peloton in a 19-man breakaway with 48 miles to go, he marked every attacking move before making a lone bid for victory in the streets of Newcastle.
"I knew that I couldn't win in a sprint, so I decided to gamble on going it alone," he said. "I chose my spot to attack at the foot of a small climb with three kilometres to go, then it was just a case of surviving to the finish."
Boardman, who ended a 10-month lean spell by winning Saturday's prologue time trial, held on to cross the finishing line Gray Street with just one second to spare.
The run-in to Newcastle had shattered the leading group, leaving 10 riders to battle for second place which went to Germany's Andre Korff with Boardman's Gan team-mate Stuart O'Grady, of Australia, in third place.
"I was as shocked as anyone, I felt rather good," he said. "If I feel the same tomorrow then I will start to believe that I've turned the corner."
Boardman now holds the Prutour's red jersey of leadership by nine seconds from George Hincapie of the US Postal team.
O'Grady moved to third overall after winning intermediate sprints at Meldo and Ponteland which carried a six- second time bonus. "I had hoped to open a few seconds overall lead with the sprint bonuses, but Hincapie was scoring as well, so I told Chris 'you're the strongest rider here, go for the stage win,'" said O'Grady.
Gan's team manager, Roger Legeay, content to have two riders in the first three overall, denied that Boardman's form had ever caused him real concern. "He was ill at the start of the season and missed the Paris-Nice. All he needs is plenty of racing and this is just the tonic he needs," he said.
The stage-winning breakaway that escaped the field in the hills north of Newcastle, could have a decisive effect on the final outcome of the 850-mile race. Racing through twisting lanes at 35mph, the escapers were soon out of sight of the main pack which finished more than five minutes in arrears and out of the reckoning for overall honours The only Britons to make the 19-man "selection" were Chris Newton and John Tanner of the Brite Voice team. Newton finished seventh on the stage to move to eighth overall. Tanner dropped off the pace in the closing stages, losing 2min 10sec for 17th overall.
Three riders made an early departure from the nine-day Tour: Stephen Russell, of Scotland, and Wim De Vos and Ben Timmermans, of the Netherlands, were disqualified and fined pounds 100 each for gaining illegal assistance by hanging on to cars.
Today's 105-mile stage from Gateshead to York, is one of the toughest of the race with first-category climbs at Westerdale and Rosedale Chimney.Reuse content