Mark Cavendish won his first British road race title after an aggressive display in a pulsating race in Glasgow.
The trio had formed part of a five-rider breakaway that forged ahead at the end of the fourth lap and was later whittled down to just three after Amy Roberts (Wiggle Honda) and then Emma Trott (Boels Dolmans) fell away.
Joanna Rowsell (Wiggle Honda) failed to join the initial move but produced a stunning late surge to claim fourth place, with Emma Trott rallying to secure fifth.
'Really special'
It is the second time Armitstead has won the national road race title, having previously claimed the British jersey in 2011, and makes up for finishing second behind Rowsell in Thursday's national time trial championships.
"It is really special," Armitstead said. "It was one of my main goals of the season. I have had an up and down season so far so I needed a bit of a confidence boost and hopefully having the jersey on my back will help."
The five escapees broke away on lap four and opened up a gap of one minute by the end of lap five, but Roberts was unable to maintain the pace and dropped back.
Emma Trott cracked two laps later after the advantage had been stretched out to 2min 40sec, but Armitstead still had more to give and surged away from Laura Trott and King on the penultimate circuit. She swiftly opened up a lead of more than 30 seconds and victory never looked in doubt.
Men's road race result
1 Mark Cavendish (Omega Pharma - Quick-Step)
2 Ian Stannard (Team Sky)
3 David Millar (Garmin-Sharp)
4 Peter Kennaugh (Team Sky)
5 Luke Rowe (Team Sky)
Women's road race result
1 Lizzie Armitstead (Boels-Dolmans) 3:12:40
2 Laura Trott (Wiggle-Honda) 1:03
3 Dani King (Wiggle-Honda) same time
4 Jo Rowsell (Wiggle-Honda) 2:58
5 Emma Trott (Boels-Dolmans) 3:20
