Bull of Union of the Greek and Latin Churches, 1439

At the Council of Florence in 1439, a papal bull was issued to proclaim the union of Eastern and Western Churches. 18 copies of this bull, issued in both Latin and Greek, survive.
The British Library’s copy contains the signature and rota of pope Eugenius IV (r. 1431-47) along with that of many Latin patriarchs and bishops, countersigned by the humanist Flavio Biondo (1392-1463). Beneath the Greek text only the signature of the emperor John VIII Palaeologus (r. 1425-48) is visible in distinctive red ink.
The document outlines the agreement reached between the Churches on a variety of doctrines. But the union, which was seen by many in the East as conceding far too much to Rome, could not last, and after the fall of Constantinople in 1453 the plan was abandoned.
The bull came into the possession of Sir Robert Cotton (1571-1631) and was grouped with other documents relating to the Church in England. Cotton’s vast collection of manuscripts was  augmented by his son, Sir Thomas Cotton (1594-1662), and grandson, Sir John Cotton (1621-1702), who bequeathed the collection to the nation. The Cotton library subsequently formed one of the foundation collections of the British Museum in 1753