id: sig-20260722-report-mm007 site_id: gb-grosmont-grosmont attribute: designation_report value: 'Reference Number MM007 Name Grosmont Castle Date of Designation Status Designated Unitary Authority Monmouthshire Community Grosmont Easting 340556 Northing 224452 Broad Class Defence Site Type Castle Period Medieval The monument consists of the remains of a castle, dating to the medieval period. Grosmont, together with White Castle (MM006) and Skenfrith (MM088), are known as the ''Three Castles'' and were held collectively. It is not known exactly when the first castle was built at Grosmont, the earliest record of it dates from 1142 although its origins probably date to the early years of the Norman conquest. The earliest castle on the site would have comprised a motte surrounded by a moat with a timber keep and timber palisade, and may have been built by William Fitz Osbern around AD 1070. The castle passed to the Marcher Lord Payn Fitz John in the early twelfth century, who gifted it to King Stephen in exchange for the province of Archenfield in 1137. It was under royal control for only two years before it was taken by Brian Fitz Count of Abergavenny in 1139. In the mid-twelfth century it was granted by charter to Walter Hereford who united it with Skenfrith and White Castle to form a single lordship. After Walter''s death in 1160 the castle reverted to royal control, under Henry II, and remained a royal fortress until 1201 when it was granted to Hubert Burgh. The mound on which the castle is built is D-shaped, curved on the south-western side and striaght on the north-eastern side. It is not clear whether this was the original shape of the motte or whether it was altered to accommodate the square hall block. Indeed, the date of the hall block is disputed with some evidence that it may have been an early feature of the castle, a rectangular stone-built keep dating from the late 11th or early 12th century, later remodelled by Hubert Burgh. Alternatively, it may have been built by Hubert Burgh as part of his extensive programme of building work that was undertaken between 1219 and 1232 when he constructed the stone fortress still visible today. The hall block is a rectangular, two storey building with four narrow lancet windows on the ground floor and thee large round-headed windows on the first floor. The ground floor would have been a store room while the upper floor would have been divided into two with the southern, larger, room functioning as the hall and the northern room the lord''s private room, or solar. There are the remains of a spiral staircase built into the south-eastern corner of the hall block, providing access from the ground floor into the main hall. On the western side of the castle the imposing curtain wall and remains of three round towers enclose the inner ward. The remains of the gatehouse are located on the south-easten side of the castle, below which can be seen the remains of the 14th century drawbridge pit. In the 14th century the castle ceased to have a military funcation and was converted to provide suitable accommodation for the Earl of Lancaster who had been granted the Three Castles by his brother, Edward I, following his subjugation of Wales. The austere, military structure was remodelled, with larger windows replacing the arrow slits of the earlier castle, fireplaces and garderobes added to the rooms in the towers, and two structures built outside the curtain wall on the northern side. The chimney of the western of the two later external structures is topped by an elaborate ashlar chimney pot and is an exceptional survival from the medieval period. The monument is of national importance for its potential to enhance our knowledge of medieval defensive practices. The monument is well-preserved and an important relic of the medieval landscape. It retains significant archaeological potential, with a strong probability of the presence of both structural evidence and intact associated deposits. The scheduled area comprises the remains described and areas around them within which related evidence may be expected to survive.' source_url: http://cadwpublic-api.azurewebsites.net/reports/sam/FullReport?lang=en&id=2343 source_title: Scheduled Monument Full Report — Grosmont Castle publisher: Cadw observed_date: '2026-07-22' collected_by: scripts/build_assessment_batch.py confidence: high notes: The designation text. Assess the six bands against THIS evidence only; omit any band it does not speak to.