Source: Embassy of Bolivia, London: "...Ex President of the Republic, Lawyer, Diplomat and Politician. Born in Sucre 5 12 1894. Parents: Mamerto Urriolagoitia and Corina Arriague Moreno. Wife: Juana Hernandez Calvo. During his period as Vice President of the Republic for the Government of Doctor Enrique Hertzog (1947-1951), due the President's resignation, he assumed constitutionally the command of the nation on the 24th October 1949, a role he had been performing already for months before. His government was distressing and unstable and the political passions exacerbated and exploited in a Civil War in August 1949. "Urriolagoitia was not a statesman of exceptional merits nor an outstanding lawyer. He was a diplomat, a man with a refined character and life, a mixture of the Basque temperament with the English spirit in which he was raised." He got to the Presidency due to a series of cicumstantial facts that have not been clarified historically yet. A close friendship linked him with the three great miners, especially to Aramayo. He imposed tough policies, mixed with other social classes and his opponents situated [sic] his politics as extreme right. In 1951 he was formed to surrender to a Military Junta to prevent the MNR, winner of the 1951 elections, assuming power, and act that history knows as the 'Mamartezo.'"

Cecil Beaton, My Bolivian Aunt: A Memoir, Weidenfeld and Nicolson, London, 1971
[p 81] The ladies of the Beni had all the time in the world for playing bridge and my aunt had become quite adept. Now she took up the game again in Maida Vale, and there was never difficulty in making up a four. New arrivals – young Secretaries at the Consulate – found their way to her flat and enjoyed her friendly company. Of these Mamerto Urriolagoitia, one of the senior Secretaries, impressed me most by his manners, his [p 82] deference to my aunt, his sense of polite amusement, and the way in which he implied that he took his career very seriously. Urrio, as he was known, had a slow smile and a fascinating mystery about the eyes – eyes that had a somewhat unseeing, slow regard – which all the dark and wide-eyed young ladies found irresistible. Even as a young man he had become almost bald, and strangely enough this gave him added distinction. I was intrigued to see that one of his thumbs was missing.