Question: Who cared for the castle with which was the caput of Lord of Liddesdale?

Context paragraphs:
William II de Soules: William II de Soules (d. 1320/1321), Lord of Liddesdale and Butler of Scotland, was a Scottish Border noble during the Wars of Scottish Independence.  William was the elder son of Nicholas II de Soules, Lord of Liddesdale and Butler of Scotland, and a cousin of Alexander Comyn, Earl of Buchan.  He was the nephew of John de Soules, Guardian of Scotland.

Feudal Barony of Berry Pomeroy: The Feudal Barony of Berry Pomeroy was one of eight feudal baronies in Devonshire which existed during the mediaeval era, and had its "caput" at the manor of Berry Pomeroy, 20 miles south of the City of Exeter and 2 miles east of the town of Totnes, where was situated Totnes Castle, the "caput" of the feudal barony of Totnes.  The exact location of the 11th-century baron's residence is unclear, perhaps it was next to the parish church on the site of the present former rectory known as Berry House, as it is now believed that the present surviving nearby ruined Berry Pomeroy Castle was not built until the 15th century.  The manor and barony was owned by the Pomeroy family from before 1086 until 1547 when it was purchased by Edward Seymour, 1st Duke of Somerset, in whose family it has since remained and today the manor and much of the former estate belongs to his descendant the Duke of Somerset, seated at Maiden Bradley House in Wiltshire.

Trematon Castle: Trematon Castle is situated near Saltash in Cornwall, England, United Kingdom.  It was the "caput" of the feudal barony of Trematon.  It is similar in style to the later Restormel Castle, with a 12th-century keep.  Trematon Castle overlooks Plymouth Sound and was built probably by Robert, Count of Mortain on the ruins of an earlier Roman fort: it is a motte-and-bailey castle and dates from soon after the Norman conquest.  It occupies a sentinel position one and a half miles south-east of Trematon village (grid reference [ SX41065801] ).

Kendal Castle: Kendal Castle is a medieval fortification to the east of the town of Kendal, Cumbria, in northern England.  The castle, which is atop a glacial drumlin, was built in the 12th century as the  Caput baroniae for the Barony of Kendal.  By the 15th century, the Parr family owned the castle.  Queen Catherine Parr  was once thought to have been born at the castle; however, modern research has shown that it was in great disrepair by the 16th century and she was most likely born in Blackfriars, London.

Hermitage Castle: Hermitage Castle is a semi-ruined castle in the border region of Scotland.  It is under the care of Historic Scotland.  The castle has a reputation, both from its history and its appearance, as one of the most sinister and atmospheric in Scotland.

William Douglas, Lord of Liddesdale: Sir William Douglas, Lord of Liddesdale (circa.  1300-k.1353) was also known as the Knight of Liddesdale and the Flower of Chivalry.  He was a Scottish nobleman and soldier active during the Second War of Scottish Independence.

Lord of Liddesdale: The Lord of Liddesdale was a magnate in the medieval Kingdom of Scotland; the territorial lordship of Liddesdale was first created by David I of Scotland, perhaps between 1113 and 1124 when the latter was Prince of the Cumbrians.  From an early period the caput of the lordship was Hermitage Castle, the "strength of Liddesdale".  King David gave the territory to Ranulf de Soules, a knight from the Cotentin Peninsula.  It was forfeited by the Soulis (de Soules) family in the 14th century and eventually passed to the Douglases, only to be lost to the Hepburns by order of James IV.  Archibald Douglas, 5th Earl of Angus was renumerated for this loss by the lordship of Bothwell Castle, although the Hepburn Earls of Bothwell retained the territorial designation

Barons in Scotland: In Scotland, a Baron is the head of a "feudal" barony (also known as prescriptive barony).  This used to be attached to a particular piece of land on which was the "caput" (Latin meaning 'head'), or the essence of the barony, normally a building, such as a castle or manor house.  Accordingly, the owner of the piece of land containing the "caput" was the Baron or Baroness.

Ayton Castle: Ayton Castle is located to the east of Ayton in the Scottish Borders.  It is 9 km north-west of Berwick upon Tweed, in the former county of Berwickshire.  Built around a medieval tower house, the present castle dates largely from the 19th century.  Ayton Castle is the "caput" of the feudal barony of Ayton.  The castle is protected as a category A listed building, and the grounds are included in the Inventory of Gardens and Designed Landscapes in Scotland, the national listing of significant parks and gardens.

Peveril Castle: Peveril Castle (also Castleton Castle or Peak Castle) is a ruined 11th-century castle overlooking the village of Castleton in the English county of Derbyshire.  It was the main settlement (or "caput") of the feudal barony of William Peverel, known as the Honour of Peverel, and was founded some time between the Norman Conquest of 1066 and its first recorded mention in the Domesday Survey of 1086, by Peverel, who held lands in Nottinghamshire and Derbyshire as a tenant-in-chief of the king.  The town became the economic centre of the barony.  The castle has views across the Hope Valley and Cave Dale.

Supporting paragraphs: Lord of Liddesdale Hermitage Castle
Answer: Historic Scotland