Fifty thousand people marched in Mexico City last weekend demanding to be told the truth about 43 students said to have been murdered by a drugs cartel with the complicity of the army while on their way to a demonstration a year ago On 26 September last year, 43 students from Ayotzinapa agricultural teacher training college, near Tixtla in Guerrero state, disappeared. They had set out by bus for the capital, Mexico City, to take part in the annual commemoration of a massacre of an estimated 600 students by Mexican armed forces on 2 October 1968. They got as far as Iguala, 88 miles away. For the past year, a storm of accusation and obfuscation has served to confuse what happened to them next.The issue has become a PR disaster for President Peña Nieto and his Government. On Saturday