Sharon Laws, who was dropped from the squad for the Olympic Games, felt she proved a point by winning the title.
The 37-year-old put the disappointment of failing to make Britain’s London 2012 team to one side to claim a solo success on the undulating 107-kilometre course through North Yorkshire.
Twenty-three-year-old Armitstead from Otley and Emma Pooley, the 2011 and 2010 champions, respectively, completed a clean sweep of the podium for AA drink leontien.nl, but were more than one and a half minutes behind Laws, who attacked on the penultimate of seven laps of a 15km route.
Armitstead and Pooley are set to ride in the July 29 road race which finishes on The Mall, with Olympic champion Nicole Cooke and Lucy Martin also selected and Laws and Katie Colclough cut as the squad was reduced to four.
Cooke (Faren-Honda) was sixth, more than nine minutes behind Laws, and Martin (AA drink leontien.nl) did not finish on a course which was far removed from the Olympic circuit.