The inhabitants of the Fen country, when first distinguished by a special name, were known as the Gyrvii.  Their district included the south part of Lincolnshire, the north part of Northamptonshire, and the greater part of Cambridgeshire.  The southern Gyrvii were a province of East Anglia; the Gyrvii of the north appear to have been allied to the East Anglians, and perhaps inclined to become united with them; but they were ultimately absorbed in the great Midland Kingdom of Mercia.  Bishop Stubbs,[29] speaking of the early Fasti of Peterborough, says:  “Mercia, late in its formation as a kingdom, sprang at once into a great state under Penda; late in its adoption of Christianity, it seems from the period of its conversion to have taken a prominent place at once among the Christian powers.  The Chronicle places the conversion in 655, and a very few years saw it the best governed and best organised province of the Church.  In less than thirty years it was divided into five dioceses, amongst which the place of the Fen country is more clearly definable.  The bishopric of Lindsey occupied the north of Lincolnshire, reaching to the Witham:  a line drawn from the south point of Nottinghamshire to the Cam would probably represent the western border of the Gyrvii; the border of Cambridgeshire was the boundary of the dioceses of Elmham and Dunwich.  The Fen country thus falls into the eastern portion of the great Lichfield diocese, which for a few years after 680 had its own bishop at Leicester, but was not finally separated from the mother see until 737.”

The date given above for the conversion of Mercia, 655, is the date of the laying of the foundation of the monastery of Medeshamstede.  Penda had been succeeded on the throne of Mercia by his eldest son, Peada; and he, in conjunction with Oswy, brother of King Oswald, determined to “rear a minster to the glory of Christ and honour of Saint Peter.”

=Saxulf= (656-675), was the first Abbot.  In Bede no mention is made of royal patronage, and the whole credit of founding the abbey is given to Saxulf.  Another account represents him as having been a thane of great wealth and renown, and that this abbey was dedicated by him “as the first fruits of the Mercian church.”  He was made Bishop of Lichfield in 675, but continued to take an active part in the affairs of the abbey.  He died in 691.

=Cuthbald= (675), is named in the Chronicle as having been second Abbot.  One of this name, possibly the same, was ruling the monastery at Oundle in 709, when S. Wilfrid died there.  Nothing further is known of him; and nothing at all of =Egbald=, who appears in the usual lists as his successor.

The chroniclers give for the fourth Abbot one Pusa.  But Bishop Stubbs has proved that =Bothwin= was Abbot from 758 to 789; and concludes that the introduction of Pusa into the list is a mistake, if not a mere invention.

Abbot =Beonna= came next, probably in 789 or very soon afterwards.  “Possibly this Beonna is the same who was made Bishop of Hereford in 823, and died in 830.”