Skipsea Castle was a Norman motte and bailey castle near the village of Skipsea, East Riding of Yorkshire, England.
 Built around 1086 by Drogo de la Beuvrière, apparently on the remains of an Iron Age mound, it was designed to secure the newly conquered region, defend against any potential Danish invasion and control the trade route across the region leading to the North Sea.
 The motte and the bailey were separated by Skipsea Mere, an artificial lake that was linked to the sea during the medieval period via a navigable channel.
 The village of Skipsea grew up beside the castle church, and the fortified town of Skipsea Brough was built alongside the castle around 1160 to capitalise on the potential trade.
Forres Castle was a fort and castle built near Forres, Scotland.
 The fort was destroyed in 850 by Vikings.
 Forres was created a royal burgh by King David I of Scotland in 1140.
 The castle, once a royal castle, was built as a motte and bailey castle and was strengthened in the 14th century.
 It was demolished in 1297 by the adherents of Wallace.
 King William the Lion and King Alexander II of Scotland visited and stayed at the castle.
 King David II of Scotland stayed at the castle in 1346.
 It was burned by Alexander Stewart, Earl of Buchan in 1390.
 Held by the Dunbars of Westfield until the 17th century, it fell into ruins.
 Nothing now remains above ground.
George Keith, 10th Earl Marischal (1692/3?
, probably at Inverugie Castle – 1778, Potsdam) was a Scottish and Prussian army officer and diplomat.
 Jacobite by persuasion, he was the tenth and last Earl Marischal, having inherited the title from his father the 9th earl in 1712.
Tretower Castle (Welsh: "Castell Tretŵr" ) is a Grade I-listed ruined castle in the village of Tretower in the county of Powys, Wales.
 It was built around the beginning of the twelfth century as a motte and bailey castle and this was probably replaced mid-century by a stone shell keep.
 The castle was enlarged in the early thirteenth century, but later fell into ruin.
Inverugie Castle or Cheyne's Tower is the ruins of a motte-and-bailey castle in Aberdeenshire, Scotland.
Thetford Castle is a medieval motte and bailey castle in the market town of Thetford in the Breckland area of Norfolk, England.
 The first castle in Thetford, a probable 11th century Norman ringwork called Red Castle, was replaced in the 12th century by a much larger motte and bailey castle on the other side of the town.
 This new castle was largely destroyed in 1173 by Henry II, although the huge motte, the second largest man-made mound in England, remained intact.
 The motte, recognised as a scheduled monument, now forms part of a local park, and the remains are known variously as Castle Hill, Castle Mound and Military Parade.
Woodwalton Castle was a small motte and bailey castle at Church End, the northern end of the parish of Woodwalton, Huntingdonshire.
 Located on a natural hillock, the earthworks of the castle still remain, with an outer moat enclosing a circular bailey with a central motte.
 A large dyke, apparently ancient, runs from the outer moat in a north-easterly direction.
 The site is a scheduled ancient monument.
Kildare Castle is a ruined castle located at Kildare in County Kildare, Ireland.
 Built in the 12th century as a motte and bailey castle by Richard de Clare, 2nd Earl of Pembroke.
 The remains of a tower are the only above ground remains of the castle.
Cardiff Castle (Welsh: "Castell Caerdydd" ) is a medieval castle and Victorian Gothic revival mansion located in the city centre of Cardiff, Wales.
 The original motte and bailey castle was built in the late 11th century by Norman invaders on top of a 3rd-century Roman fort.
 The castle was commissioned either by William the Conqueror or by Robert Fitzhamon, and formed the heart of the medieval town of Cardiff and the Marcher Lord territory of Glamorgan.
 In the 12th century the castle began to be rebuilt in stone, probably by Robert of Gloucester, with a shell keep and substantial defensive walls being erected.
 Further work was conducted by Richard de Clare, 6th Earl of Gloucester, in the second half of the 13th century.
 Cardiff Castle was repeatedly involved in the conflicts between the Anglo-Normans and the Welsh, being attacked several times in the 12th century, and stormed in 1404 during the revolt of Owain Glyndŵr.
Hangthwaite Castle was an earthwork motte and bailey castle founded by Nigel Fozzard.
 It stood in the 11th century and is situated just north of Scawthorpe, Doncaster, South Yorkshire, England.
 In the 13th century, a fortified house called Radcliffe Moat ( ) replaced Hangthwaite Castle as a local fortification.
 Nowadays, only the motte and the ditches remain.
 Encased by the wide wet ditch, the motte defends a bean-shaped eastern bailey and a small north-western mound, which is possibly a barbican.

Question: George Keith was probably the last Earl Marishal at what ruined motte and bailey castle in Aberdeenshire, Scotland?
Answer: Inverugie Castle