The Benedictine Abbey of St. Peter of Chertsey was founded in the yeare A.D. 666 by Erkenwald, afterwards Bishop of London, who became its first abbot, the new foundation being endowed with lands by the munificence of Frithwald, Subregulus of Surrey, under Ulfar, King of the Mercians, who in subsequent accounts is associated with Erkenwald as co-founder. In the first charter of the foundation Frithwald recites that, for the augmentation of the monastery first built under King Egbert, he had granted 200 dwellings and 5 dwellings in a place called Thorpe to Erkenwald the abbot. This charter was witnessed and confirmed by King Ulfar and specifies the boundaries of the donation. A charter of privileges granted by Pope Agathon (678-82) was brought personally from Rome by the abbot then raised to the metropolitan see. Subsequent kings confirmed the possessions of the monastery: Offa, King of the Mercians, in 787, at the request of Cynedritha his queen, and Ceolnod the abbot; Ethelwulf in 827; and King Athelstan in 993.
From the yeare 850, and onwards through the ninth century, the monastery shared the perils of the country threatened by the incursions of the Danes. This contact with national history is reflected in the pages of their chronicle; it narrates the story of the struggle against the heathen, describes the dangers to which all the coasts were exposed, and in particular the counties of Kent, Surrey and Sussex, the fruitless efforts of the kings, the death of King Ethelbert 'broken with many labours,' and culminates in the account of the attack on the monastery itself, the slaughter of Beocca the abbot, Ethor the priest, and ninety monks, their home burnt down, and their lands wasted.
Many years elapsed before the work of restoration was begun. Then Ethelwald, Bishop of Winchester (936-84), sent to the abbot and convent of Abingdon commanding that thirteen monks be sent to colonise a new house on the old site. There they elected one of their number abbot, and a new church was raised. It was also divinely revealed to a certain monk that the bodies of those who had been slain by the heathen should be removed from the place where they were resting and honourably collected and placed in a wooden shrine, which was accordingly done. The new colony however, did not remain long undisturbed. In 964 King Edgar, inflamed by the reforming zeal of Dunstan, drove forth the inmates sent by Ethelwald and established regulars there with Ordbright as their abbot. After these vicissitudes the house seems to have entered upon a period of ease and prosperity wherein its borders became enlarged. Edward the Confessor certified by charter to Stigand the archbishop and Harold the earl that he had granted to Christ and St. Peter of Chertsey that town with the towns of Egham, Thorpe and Chobham, and that the abbot and convent should have soc and sac, tol, theam and infangnethef within all their manors, and also confirmed the gift by a previous charter of the Hundred of Godley. The 'Saint of England' further added to the endowment the village and church of White Waltham, Berks, with woods and 20 acres of pasture at Cookham.
The house seems to have enjoyed the favour and protection of the Conqueror, who confirmed the possessions which the abbot and convent held in the time of King Edward with soc and sac, and conferred on them rights of warren, liberty of the chase, the right to keep dogs, and take hares, foxes, etc., within all their lands in Surrey, with a mandate addressed to the sheriff, the king's foresters and ministers that the abbot and convent should not be molested. The Domesday Survey shows that the estates held by the abbey were already very considerable and not confined to the county of Surrey alone, and they were later increased by further donations from the descendants of the Conqueror.
Royal favour was accompanied by support from Rome. Pope Alexander III., recalling the privileges accorded by his predecessors, confirmed to the abbey the tithes of Chertsey, Egham , Thorpe and Chobham, and ordained that the abbot should not retain them in his own hands, or expend them in other uses, but that they should be applied by two honest men to the repair of the abbey and the maintenance of its offices. The Welsh priory or cell of Cardigan with its appurtenances, the churches of Holy Trinity and of St. Peter of 'Berwyke,' the chapels of St. Peter of Cardigan and St. Michael of Tremain which had been granted to the abbey by Rees Ap Griffin, Prince of South Wales, for his soul, and the souls of his wife, his parents and his sons, was confirmed by successive bulls of the popes, Alexander III. and IV. Alexander III. also forbad the promulgation of any sentence of interdict or excommunication on any abbot or monk, and Alexander IV. enacted that the chrism, holy oil, consecration of altars or churches, and ordination of clerks should be undertaken by the diocesan bishop, and forbad that any chapel or oratory should be built within the bounds of the parish save by the consent of the abbot and diocesan.
During the thirteenth and fourteenth centuries the abbey was engaged in many disputes, the settlement of which, involving litigation and papal arbitration, must have greatly taxed its already diminishing resources. Finally in the case of disputes involving but slight issues the house resorted to less official mediation 'in order to save extortion.' Up to the end of the thirteenth century there was a marked absence of appropriation in connection with this house.
The taxation roll of 1291 shows that the annual value of the various Surrey manors of the abbey amounted to £135 19s. 8d. There was in addition an income of £7 0s. 7d. from temporalities in seven London parishes, and £7 from the diocese of Salisbury. The only spirituality reckoned is a pension of £1 19s. from a London church. The monastery probably began to realise the fluctuating nature of the greater part of an income derived mainly from land and subject to agricultural depression, and sought to remedy this distress by resort to appropriation. The Bishop of Winchester in 1292 permitted the abbot and convent to retain to their own uses the church of Bookham which was of their patronage, then void by the resignation of John of London, the late rector, so that they presented a suitable person to perform divine service there. It was stated as a reason for this concession that the funds of the monastery had of late materially decreased by exactions, by pestilences, and by inundations of water that affected animals, flocks, and other property of Chertsey.
The grant which was confirmed by the Crown, recited the permission granted to the abbey by Pope Clement III. in 1190 whereby they might retain in their own hands the parish churches of Bookham, Epsom, Ewell, Waltham, Horley, Cobham, and Coulsdon, and the chapels of Chertsey and 'Wetesdon.' In 1313 licence was obtained from the king for the appropriation of the churches of Horley and Epsom, and in 1380 Richard allowed the convent to appropriate the church of Ewell, the three churches being already of their advowson. John de Benham obtained the church of White Waltham, Berkshire, in 1348.