Defending champion Bjarne Riis could find that today's 12th stage time trial in St Etienne effectively ends his reign as Tour de France champion and heralds that of team-mate Jan Ullrich.The young usurper Ullrich (23), breaking the shackles of loyalty to his team leader, took a commanding lead in the tough 10th stage in the Pyrenees on Tuesday when he left Riis and other contenders for dead.That showed he had the strength to succeed the veteran Dane as champion.Now, with other pre-Tour favourites either out of the running or of the race altogether, the pressure is on Riis to keep tabs on the talented German, who is looking to replace Miguel Indurain, also brilliant in the time trials, as Tour king.Gone is Swiss veteran Tony Rominger, who broke his collarbone in the third stage and was the only rider with a better average speed in a Tour time trial than Ullrich.French mountain specialist Richard Virenque, second overall two minutes 38 seconds behind Ullrich, has been improving in the solo tests against the clock, over the years as he seeks to become France's first winner since Bernard Hinault in 1985."Ullrich will have an advantage in the time trial. But the Alps are very difficult and should favour climbers like me or (Italian Marco) Pantani," said Virenque.Ullrich, although not a noted climber, added to his aura of an all-powerful rider in the Pyrenees and victory in the time trial should be enough for a Tour triumph.