William FitzOsbern, Norman Count of William the Conqueror, established Monmouth Castle between 1066 and 1069 as a counterpart to his other major castle at Chepstow. It was originally an earth and timber ringwork fortress, which was listed in the Domesday Book. The wooden castle had stonework added before 1150.
After briefly being held by Simon de Montfort, 6th Earl of Leicester, Monmouth Castle passed into the hands of Edmund Crouchback, Earl of Lancaster and son of Henry III in 1267. He redeveloped the castle, building the Hall and took it as his main residence in the area. It was further improved in the early 14th century, probably by Crouchback's grandson, Henry of Grosmont, 1st Duke of Lancaster. During this period large decorated windows were installed in the upper part of the Great Tower which also had a new roof. As a town developed around the castle, the castle's defences were augmented by a town wall and fortified bridge, built at the end of the 13th century.
Edward II briefly was held prisoner in the castle before he was transferred to Berkeley Castle where he died. The castle was a favourite residence of Henry Bolingbroke, later King as Henry IV. It was here that in 1387 the future King Henry V of England was born, to Bolingbroke's first wife Mary de Bohun.
Over the centuries, as its defensive function diminished, the outer bailey of the castle became increasingly used as a market place, later (and now) known as Agincourt Square. During the sixteenth century, when Monmouth became the county town of the newly formed shire of Monmouth, the county's Courts of Assize began to be held in the castle's Great Hall.
In the tumult of the English Civil War, Monmouth Castle changed hands three times, finally falling to the Parliamentarians in 1645. Oliver Cromwell visited Monmouth in 1646, and according to tradition ordered the slighting (demolition) of the castle. Great Castle House was built in 1673, on the site of the old round tower, by Henry Somerset, 1st Duke of Beaufort.
Only fragments of the castle, including the Great Tower and Hall and parts of the walls, remain above ground, and on the site Castle House and Great House have been built. In 1875, the Royal Monmouthshire Royal Engineers Militia, the senior Territorial Army regiment today, made it their Headquarters building and so it remains. It is one of the few British castles in continuous military occupancy. The Royal Monmouthshire Royal Engineers museum is located in the stable block attached to Great Castle House. It includes exhibits relating to the history of the regiment from 1539 to the present day.
References:Saint-Georges de Boscherville Abbey is a former Benedictine abbey. It was founded in about 1113 by Guillaume de Tancarville on the site of an earlier establishment of secular canons and settled by monks from the Abbey of Saint-Evroul. The abbey church made of Caumont stone was erected from 1113 to 1140. The Norman builders aimed to have very well-lit naves and they did this by means of tall, large windows, initially made possible by a wooden ceiling, which prevented uplift, although this was replaced by a Gothic vault in the 13th century. The chapter room was built after the abbey church and dates from the last quarter of the 12th century.
The arrival of the Maurist monks in 1659, after the disasters of the Wars of Religion, helped to get the abbey back on a firmer spiritual, architectural and economic footing. They erected a large monastic building one wing of which fitted tightly around the chapter house (which was otherwise left as it was).