LONDON (Reuters) - American Matt Grevers posted the fastest qualifying time for the men's 100 meters backstroke at the London Olympics on Sunday.

Grevers, who was runner-up to his countryman Aaron Peirsol at the Beijing Games, steamed to victory in 52.92 seconds, conserving plenty of energy for the 4x100 freestyle relay heats, which were held in the same session.

China's Cheng Feiyi was second overall while Grevers' compatriot Nick Thoman was third fastest. World champion Camille Lacourt of France was fourth.

Lacourt's joint world champion Jeremy Stravius, the pair dead heated in Shanghai, did not qualify for the Olympics after finishing third at the French trials earlier this year.

Grevers is the latest in a long line of great American backstrokers but spent most of his career in the shadows of Peirsol before succeeding his mantle when he retired.

(Reporting by Julian Linden; Editing by Greg Stutchbury)