The Kremlin's most prominent critic Alexei Navalny was in a Moscow courtroom yesterday facing several years in prison, after his arrest last month triggered protests across Russia and Western condemnation. The 44-year-old anti-corruption campaigner was detained on January 17 when he returned to Moscow from Germany, where he had spent months recovering from a nerve agent poisoning in August that he blames on President Vladimir Putin. Tens of thousands have taken to the streets of Moscow and other cities over the last two weekends to call for Navalny's release, prompting a massive police clampdown that saw several thousand people arrested. The case is presenting one of the most serious challenges to the Kremlin in years and has led to calls for new Western sanctions against Russian authorities.