Tour de France favorite Bradley Wiggins began his attempts to become the first British winner of the yellow jersey with a second placed finish in the opening day prologue in Liege.
The Team Sky rider, a time trial Olympic champion on the track, led going into the closing stages, only to see Switerland's Fabian Cancellara snatch victory away; bettering the Brit's time by seven seconds.
Defending champion Cadel Evans began his campaign with a 13th place finish, with 9.5 seconds separating him from Wiggins heading into day two's Seraing stage.
Cancellara said: "Every victory is important but today was special after a hard comeback (after breaking his collarbone in the Tour of Flanders in April). I've done what I had to do today. I was motivated and it's a victory I won't forget for a long time."
The day firmly belonged to Cancellara, who as well as taking his fifth prologue win in Tour history to secure the yellow jersey for day two - a feat only matched by Bernard Hinault - he laid down a maker for the upcoming time trials over the next three weeks, and for the Olympic Games in London.
Wiggins will also compete in the English capital against the Swiss, and despite starting in cautious fashion, finished strongly to topple Omega Pharma rider Sylvain Chavanel, who led for long stages of the opening day.
Fellow Brit David Millar overcame a mid-week illness to finish in 7 minutes and 31 seconds, in 16th, alongside Stephen Cummings, both of whom are 18 seconds behind Cancellara.
World time trial champion Tony Martin will meanwhile be thinking what if after seeing a mechanical failure force him to change bikes mid-way through his time trial, before finishing 23 seconds off the pace.
Spearheaded by Wiggins, Team Sky enjoyed a decent opening day with Edvald Boasson Hagen finishing fifth, Chris Froome came in in 11th, Christian Knees in 27th and Ritchie Porte in 36th.
Mark Cavendish, defending green jersey from 2011, finished 41st overall, Australian Michael Rogers in 61st, Sivtsov Kantastsin 63rd and Bernhard 101st.
Home favorite Philippe Gilbert goes into Seraing's 2.5km ascent as favorite to win the second stage as the Tour remains in Belgium on day two.