Sydenham was settled in the
Anglo-Saxon era. Its
toponym means "at the wide river-meadow". Before the
Norman Conquest of England a
Saxon called Almar held the
manor of Sydenham. After the conquest
William the Conqueror granted the manor to
William FitzOsbern, 1st Earl of Hereford. In 1075 FitzOsbern's son
Roger de Breteuil, 2nd Earl of Hereford was one of the leaders of the
Revolt of the Earls. After the rebellion's failure William I confiscated all of Roger's lands, including Sydenham. In the 12th century the de
Vernon family who held the manor of
Chinnor held also a small estate at Sydenham. Richard de Vernon granted one
hide of land at Sydenham to the
Cistercian Thame Abbey by 1146 and a second hide by 1155. In 1203 the manor of Sydenham was granted to
Saer de Quincy, 1st Earl of Winchester. In 1248 his son
Roger de Quincy, 2nd Earl of Winchester gave the manor of Sydenham to Thame Abbey. The Abbey held the manor and Sydenham Grange until
the Crown forced it to surrender all its property in the
Dissolution of the Monasteries in 1539. In 1542
the Crown granted Sydenham to Sir John Williams, who in 1554 was made
Baron Williams de Thame. In 1559 Baron Williams died without a male heir, leaving his estates to be divided between his two daughters. He left Sydenham to his daughter Margaret and her husband Henry Norris, who in 1572 was created
1st Baron Norreys. In 1608 Henry Norris' heir
Francis Norris, 1st Earl of Berkshire conveyed Sydenham to Sir Richard Wenman, who in 1628 was created
1st Viscount Wenman. The Manor of Sydenham remained with the Wenmans and their heirs the Wykeham-Musgraves until early in the 20th century. Between 1917 and 1925 the family sold almost all of the manor, and the manorial rights lapsed. There were some early
enclosures of land in the parish: Thame Abbey's Sydenham Grange existed by 1474, and further enclosures had taken place by the 1550s and 1630. However, half of the land of the parish continued to be farmed under an
open field system until the
Thame and Sydenham Inclosure Act 1823 (
4 Geo. 4. c.
8 ) was passed, leading to an enclosure award in 1826. ==Church and chapels==