Sandleford Priory was a small Augustinian Priory, the remains of which now stand at Sandleford in the civil parish of Greenham in the English county of Berkshire.

History Archbishop (and Cardinal) Stephen (Langton) (c.1150–1228) (Archbishop of Canterbury, 1207–1228), in its confirmation charter stated that the house was dedicated to the honour of St. John Baptist (and the Blessed Virgin Mary and all the Saints). The original seals on the charter featured those of the Archbishop of Canterbury Hubert Walter, the Bishop of Sarum Herbert le Poer (Poore), William of Perche (died 1226) bishop of Châlons, and Stephen of Perche (killed in 1205);Walter Money, FSA, A history of the ancient town and borough of Newbury, in the county of Berkshire, Parker & Co., Oxford & London, 1887, page 60.

The Priory of St John the Baptist at Sandleford was founded for the Augustinian Canons Regular by Geoffrey, Earl of Perch and his wife Maud some time between 1193 and 1202.

In 1274, Maud de Clare, Countess of Gloucester and Hertford made arrangements to refound it as a double house for Fontevrault Benedictine nuns and brothers, but this did not come about. It was dissolved in 1478 and abandoned by the remaining monks after years of mismanagement by a prior. The ownership fell into the hands of the Bishop of Salisbury, and circa 1480 passed to the Dean and Chapter of Windsor. The old priory chapel is the present library. The remains were converted to a country house.

On 31 August 1320, King Edward II was at Sandleford Priory, where he apparently tarried for the night.Walter Money, Newbury, page 160

One of the last of the priors was a man named Simon Dam who was dismissed after he was caught with his mistress, Thomasina, at the Priory in 1440.

The number of canons at the priory eventually dwindled until at the death of the last prior in 1478 when there were none left.

Priors Walter, occurs (presented or elected) July 1222;The Heads of Religious Houses: England and Wales, II. 1216–1377, edited by David M. Smith, Vera C. M. London, Cambridge University Press, 2004, page 457. John, occurs circa 1230-1240; Gervase, occurs 1255; Stephen, occurs 1256-1262; Robert de Winchester (Wynton or Winton), elected or there 1301; Thomas de Sandleford, occurs 1311, 1330; William de Wynton (Winchester), resigned 1334; Robert [Gilbert], 1334, and occurs 27 January 1336/7; John, occurs 2 February 1354/55; John, occurs 11 February 1383/84; Richard Stanford, elected 1403; Hugh Warham, elected 1406, a kinsman of William Warham (c.1450–1532); Symon Dam, deposed 1439/1440; William Costyn, elected 1448, formerly a canon of Bisham Abbey; William Westbury, occurs 1457.VCH First headmaster of Eton College 1442–1447, and then its fourth Provost 1447–1477. Provost Westbury saved Eton from amalgamation with St. George's Chapel, Windsor.A History of Eton college, by Lionel Cust (1859–1929), Duckworth, London, 1899, page 20.The Life of William Waynflete, Bishop of Winchester,, etc, by Richard Chandler, D.D., London, 1811.

Patrons

Anglo-French magnate and veteran of the Third Crusade Geoffrey (died 1202,Walter Money, FSA, A history of the ancient town and borough of Newbury, in the county of Berkshire, Parker & Co., Oxford & London, 1887, page 62. buried St. Denis, Nogent-le-Rotrou), Earl of Perche and Mortagne, of the House of Châteaudun, Lord of the manor of Newbury, and his wife (they married in 1189) Richenza-Matilda of Saxony, daughter of Henry the Lion, duke of Bavaria and duke of Saxony, (died 1195) by Matilda (or Maud) of England (died 1189). Matilda, countess de Perche, was thus a legitimate granddaughter of King Henry II (died 1189) and Eleanor of Aquitane (died 1204), a great-granddaughter of Empress Matilda (died 1167), great-great grand daughter of Matilda of Scotland (died 1118), and was niece of both King Richard the Lionheart (died 1199) and Bad King John (died 1216), and of Queen Eleanor of Castille (died 1214). The Holy Roman Emperor Otto IV was one of Matilda's brothers. In 1204, two years after count Geoffrey's death, Richenza-Matilda married Enguerrand III, Lord of Coucy (c.1182–1242), Enguerrand le Grand, of Picardy.

Matilda and Geoffrey III, fourth Count of Perche, founded Sandleford Priory between 1193 and 1200. In addition to the freehold of the site and 600 or so acres, all the lands at Sandleford, as it is bound by hedges and ditches, with all its appurtenances, an annuity of 13 marks from the mills of Newbury was allocated for the support of the house.A History of the County of Berkshire: Volume 4, Victoria County History, London, 1924. Geoffrey's grandfather the great Rotrou III, Count of Perche (1084-killed 1143/44) married (1136) Hawise (Harwise or Hedwig) d'Evereux (1118–1152), daughter of Walter (d'Evereux) of Salisbury by Sibyl de Chaworth (de Chaources, alias Mundublel, alias de Cadurcis). Sibyl's parents who married in 1118 were Maud/Matilda de Hesdin and Patrick de Chaources. Sibyl was thus a granddaughter of the modern era founder of Newbury the Lord of Ulvritone, Ernulf de Hesdin (died Antioch, 1097). Hawise was an elder sister of Patrick of Salisbury, 1st Earl of Salisbury (c. 1122 – 1168) and of Sibyl Marshal. Hawise and Rotrou III's son, Count Geoffrey's father, Rotrou IV, count of Perche and Mortagne,sometimes written Montague: perhaps a fanciful connection that drew Edward Montagu to lease Sandleford over 500 years later? In addition by 1700 the Earldom of Salisbury had been revived for a branch Montagu family. was slain during the Third Crusade at the Siege of Acre, having married Matilda (died 1184) daughter of Theobald IV. Hawise's younger sister Sibyl (1120-) married John Marshal, and their sons John the Marshall, William Marshal, 1st Earl of Pembroke and Henry Marshall (bishop of Exeter) (died 1206) were thus Geoffrey's first cousins-once-removed. After Count Thomas Perche's death, at the Battle of Lincoln leading the forces of the Capetain Prince Louis against King John and his noble cousin William Marshal, 1st Earl of Pembroke (died 1219) in 1217, his noble kinswoman, a second cousin once removed, Ella or Ela of Salisbury, 3rd Countess of Salisbury, daughter of William of Salisbury, 2nd Earl of Salisbury, and wife of William Longespée (Longspey), 3rd Earl of Salisbury claimed some of his property, including Newbury. William Longspey, Lord Salisbury, was uncle of Henry III.The Counts of the Perche, 1066–1217, Dr. Kathleen Hapgood Thompson, Sheffield, 1995. The connection of John le Marshal (died 1194) and his younger brother William Marshal, 1st Earl of Pembroke (died 1219), of Newbury Castle, Hamstead Marshall to Sandleford also shown by the former's mistress Alice de Colville (died before 1220?) of Maidencourt, East Garston giving six-quarters of wheat (28 pounds x 6 = 168 pounds = 12 stone) from Maidencourt to the Priory of Sandleford for praying for their souls.VCH, Berks, vol. 4, East Garston. The VCH assertion of son changed to brother by work of David Crouch in "William Marshal, knighthood, war and chivalry 1147–1219", 2nd edition, 2002, pages 89–90, and by Douglas Richardson. Geoffrey's uncle Stephen du Perche (1137/8–1169), had been Archbishop of Palermo, and his brother Stephen was killed at siege and Battle of Adrianople in 1205, while two other brothers, Rotrou (bishop 1190–1200) and William (died 1226), were both sometime bishops of Châlons.Walter Money, FSA, A history of the ancient town and borough of Newbury, in the county of Berkshire, Parker & Co., Oxford & London, 1887, page 62. In 1195 Geoffrey was described by the chronicler as a man whose soul was naturally grand and magnanimous [whose] sole happiness was to consecrate his fortune in fostering religion and relieving suffering humanity [in conjunction with] his noble and pious wife Matilda.Walter Money, FSA, A history of the ancient town and borough of Newbury, in the county of Berkshire, Parker & Co., Oxford & London, 1887, page 63. Despite the royal status of the widow Countess Matilda, her uncle King John, around 1204, soon after death of the Count Geoffrey Rotrou of Perche in 1202 (Geoffrey had he not died would have taken part in the Fourth Crusade,Thompson, 2013) started to repossess and reassign the lands of the Perche in England. Dr. Kathleen Thompson says (2013): However, the king went to some lengths to preserve the Rotrou family association with the lands. He guaranteed two pensions which Count Geoffrey had granted from the revenues of Newbury, ordering that Simon of Pattishall was to be reimbursed for their continued payment, and instructed Simon to honour Count Geoffrey's grant of a rent from the mill at Newbury to the canons of Sandleford.Power and Border Lordship in Medieval France, The County of the Perche, 1000–1226, Dr. Kathleen Thompson, Boydell, 2013, page 183

Alice de Colville (died before 1220?) of Maidencourt, East Garston. Gave six-quarters of wheat (28 pounds x 6 = 168 pounds = 12 stone) from Maidencourt to the Priory of Sandleford for praying for the souls of John le Marshal (died 1194) and his younger brother William Marshal, 1st Earl of Pembroke, of Newbury Castle, Hamstead Marshall, etc.VCH, Berks, vol. 4, East Garston. The VCH assertion of son changed to brother by work of David Crouch in "William Marshal, knighthood, war and chivalry 1147–1219", 2nd edition, 2002, pages 89–90, and by Douglas Richardson. Maud de Clare, (1223–1289), was daughter of John de Lacy, 2nd Earl of Lincoln, and the wife of Richard de Clare, 5th Earl of Hertford, 6th Earl of Gloucester, conceived at Sandleford, with help of a Papal mandate dated 1274, an Augustinian convent for 40 nuns and for 10 priests of the order of Fontevraud Abbey;From VCH, Berks.: It appears, however, that Maud de Clare, Countess of Gloucester and Hertford, learning that the house was occupied by three Augustinian canons without abbot or prior, conceived the project of founding a convent for forty inclosed nuns under the rule of St. Augustine and, in a place apart, for ten priests of the order of Fontevraud, at Sandleford in the diocese of Salisbury. She was prepared to increase the endowment from £100 to £200, directing that one of the priests should act as prior with the assent of the abbots (sic) and nuns. A papal mandate of 1274 directed the fulfilment of her intentions. Her husband was a grandson of William Marshal, 1st Earl of Pembroke. Her granddaughter, Elizabeth de Clare, founded Clare College, Cambridge in 1338.