Cyclist Lizzie Armitstead and swimmer Rebecca Adlington have won Great Britain's first medals of the London 2012 Olympic Games.

Adlington, 23, won a bronze medal in the women's 400m freestyle final, which was won by Camille Muffat of France.

Earlier, Armitstead banished the disappointment of the men's road race as crowds billowing "Lizzie, Lizzie" swept her to silver.

Union Jack flag-waving fans lined the home straight of the 140km women's road race despite the traditionally British weather, banging the hoardings as Armitstead secured her place on the podium.

"It's something very special and it hasn't sunk in yet," she said. "I'm really, really happy. Maybe later I'll start thinking about that gold, but I'm happy with silver at the moment."

Her mother Carol said she was "so proud" of her silver medal in the women's cycling road race, adding: "It is more than we can have hoped for."

But Britain's marathon world record holder Paula Radcliffe's Olympic dream was over as she was ruled out through injury. "It hurts so much to finally admit to myself that it isn't going to happen," the 38-year-old said after a foot problem flared up again.

It came as London 2012 organisers again called in the troops, this time to help prevent Olympic venues from looking empty. Servicemen and women, widely praised for stepping in when private firm G4S failed to supply enough guards, were asked to help out again by watching the Games and filling seats in their rest periods.

An urgent investigation was launched after gaps were visible at a number of sites on the first full day of competition yesterday, including the Aquatics Centre where British medal hope Hannah Miley missed out on a podium place.