The term “The Three Castles” is used to collectively describe White Castle, Skenfrith Castle and Grosmont Castle, all of which are located in the Monnow Valley in south Wales (modern day Monmouthshire).
The Monnow Valley was an important route between Hereford and Monmouth in medieval times, due to its position as an area of relatively open land, which provided a break between the river cliffs of the Wye Valley to the south, and the hills around Abergavenny to the west.
Fitz Osbern died in 1071, and his lands were forfeited to the crown after his son Roger de Breteuil was involved in a rebellion against King William in 1075.
Later the king divided up this strategically important territory – the only time in their active history that the Three Castles were owned separately.
White Castle was given to the State in 1922, followed by Grosmont in 1923.
Skenfrith passed through several hands before being given to the National Trust.
The first defences were built shortly after the Norman Conquest of 1066, although the remains of the castle that stand today date from the early thirteenth century.