After the Romans left Britain in the early 5th century, the Brythons re-established control but the territorial divisions for the post-Roman period are uncertain.
The English conquest of the Severn valley began in 577 with the victory of Ceawlin at Deorham, followed by the capture of Cirencester, Gloucester and Bath.
Towards the close of the 11th century, the boundaries were readjusted to include Winchcombeshire, previously a county by itself, and at the same time the forest district between the Wye and the Severn was added to Gloucestershire.
[2] Gloucestershire formed part of Harold's earldom at the time of the Norman Conquest of England, but it offered slight resistance to William the Conqueror.
[2] Two Civil War battles were fought at Beverston Castle, and Parliament ordered its battlements destroyed to deprive the Royalists use of the fortress.
[8] On the subdivision of the Mercian diocese in 680 the greater part of modern Gloucestershire was included in the diocese of Worcester,[9] and shortly after the Conquest constituted the archdeaconry of Gloucester, which in 1290 comprised the deaneries of Campden, Stow, Cirencester, Fairford, Winchcombe, Stonehouse, Hawkesbury, Bitton, Bristol, Dursley and Gloucester.
The Berkeleys have held lands in Gloucestershire from the time of the Domesday Survey, and the families of Basset, Tracy, Clifton, Dennis and Poyntz have figured prominently in the annals of the county.
[15] The hill district, besides fostering agricultural pursuits, gradually absorbed the woollen trade from the big towns, which now devoted themselves almost entirely to foreign commerce.
[17] The abundance of clay and building-stone in the county gave rise to considerable manufactures of brick, tiles and pottery.
Numerous minor industries sprang up in the 17th and 18th centuries, such as flax-growing and the manufacture of pins, buttons, lace, stockings, rope and sailcloth.
Of the abbey of Hailes near Winchcomb, founded by Richard, Earl of Cornwall, in 1246, little more than the foundations are left, but these have been excavated with great care, and interesting fragments have been brought to light.
The Perpendicular church at Lechlade is unusually perfect; and that at Fairford was built (c. 1500), according to tradition, to contain the remarkable series of stained glass windows which are said to have been brought from the Netherlands.
Thornbury Castle, in the same district, is a fine Tudor ruin, the pretensions of which evoked the jealousy of Cardinal Wolsey against its builder, Edward Stafford, 3rd Duke of Buckingham, who was beheaded in 1521.