Newcastle Castle was initially constructed as a ringwork 1106 by William de Londres, one of the legendary Twelve Knights of Glamorgan, as part of the Norman invasion of Wales. William de Londres was a knight loyal to the Norman baron Robert Fitzhamon and the Newcastle defences marked the most western extent of Fitzhamon's lordship.
The defences were strengthened either by William Fitz Robert, 2nd Earl of Gloucester, shortly before his death in 1183 or by Henry II who took over the lordship of Glamorgan on William's death. The additional works had the construction of a 2-m-thick curtain wall which surrounded a courtyard which was 40 m in length. The main reason behind these new defences was believed to be a response to the uprising in Glamorgan led by the Welsh Lord of Afan, Morgan ap Caradog. Henry died in 1189, and the ownership of Newcastle fell to Prince John, who that year handed the castle to Morgan ap Caradog. When Morgan died circa 1208, he was succeeded by his son Lleison. On Lleison's death, thought to be around 1214, the castle came into the ownership of Isabel, Countess of Gloucester, the first wife of King John. In 1217, the ownership changed again, staying briefly with the Anglo-Norman baron Gilbert Fitz Richard, who in the same year handed the castle over to Gilbert de Turberville, who preferred to continue living at Coity Castle.
The castle is notable for the high quality of the stonework, especially that of the Norman doorway. This is late 12th century, and was likely constructed at the same time as the high curtain walls and the two square towers which they support. Only the base of the west tower survives, but the south tower has three storeys. This was remodelled for living quarters in the 16th century, when Tudor windows and fireplaces were added.
Newcastle Castle is under the care of Cadw. It is open free of charge throughout the year.
References:Ehrenbreitstein Fortress was built as the backbone of the regional fortification system, Festung Koblenz, by Prussia between 1817 and 1832 and guarded the middle Rhine region, an area that had been invaded by French troops repeatedly before. The fortress was never attacked.
Early fortifications at the site can be dated back to about 1000 BC. At about AD 1000 Ehrenbert erected a castle. The Archbishops of Trier expanded it with a supporting castle Burg Helferstein and guarded the Holy Tunic in it from 1657 to 1794. Successive Archbishops used the castle's strategic importance to barter between contending powers; thus in 1672 at the outset of war between France and Germany the Archbishop refused requests both from the envoys of Louis XIV and from Brandenburg's Ambassador, Christoph Caspar von Blumenthal, to permit the passage of troops across the Rhine.