Trelawny entered the Royal Navy at the age of eleven, only to desert and lead a life of adventure (described in his Adventures of a Younger Son, 1831). In 1821 he met Percy Bysshe Shelley and Byron in Pisa. After Shelley's death, Trelawny supervised the cremation of his body, and helped to raise enough money to allow Mary Shelley to return to England. In 1823 he went to Greece with Byron to assist in the struggle for Greek independence. Trelawny describes his friendship with Shelley and Byron in Recollections of the Last Days of Shelley and Byron (1858), republished as Records of Shelley, Byron, and the Author in 1878.