Armesto played Charles V, Holy Roman Emperor in the series The Tudors. He starred in the 2008 ITV drama series The Palace as the King's carefree younger brother Prince George. He then played the character of Edmund Sparkler in the 2008 BBC version of Charles Dickens' novel Little Dorrit. In the 2011 film Pirates of the Caribbean: On Stranger Tides Armesto played the Spanish King Ferdinand VI. He plays the poet and Playwright Ben Jonson in Roland Emmerich’s feature film Anonymous.