Veteran Australian cyclist Stuart O'Grady finished fourth behind British winner Mark Cavendish in the Olympic road race test event in London.

The 140km race was a shortened version of the 250km Olympic event on the London-Surrey circuit that will be held on July 28 next year.

Britain's Tour de France sprint ace Cavendish won from Sacha Modolo of Italy and Samuel Dumoulin of France with O'Grady the best-placed Australian.

Matt Goss was next best of the five-man Australian team in eighth place.

Compatriots Leigh Howard (70th), Heinrich Haussler (71st) and Michael Matthews (78th) were down in the pecking order.

The race started on The Mall in central London before heading into Surrey and then returning to The Mall for the finish.

Cavendish told the BBC: "You can't get a sense of how the 2012 race will go, but you can get a feel for this course and the route is good."

AAP