GUZMÁN, Gaspar de, Conde de Olivares (1587-1645). Autograph letter signed to an unidentified recipient, n.p., 3 September 1626, referring to a document that will prove his innocence in an affair relating to the King, one page, folio, on a bifolium, mounted at edges. Olivares was Philip III's ambassador to Rome, and favourite and valido to Philip IV, directing Spain's foreign policy for twenty-two years. By the time of the present document Olivares's power had waned, following prolonged periods of war, and in 1643 he was finally driven from office by the Spanish court and Queen Isabella.