The surname Cobelstone was first found in Devon at Coplestone (Copelstan.) "From the Copelanstan these three hides afterwards took name, and they were granted, as an endorsement on the original charter certifies, by the venerable priest Brihtric to the minster of Crediton, some time before the Norman Conquest. At an unknown but very early period, however, the estate passed into the hands of one of the oldest of Devonshire families, who thence took name, and who proudly held themselves to be descended from an English ancestor who kept his lands through the Conquest, the ancient rhyme running :
' Crocker, Cruwys, and Coplestone,
When the Conqueror came were found at home.'
"These families fill a prominent place in Devonian history ; but neither can be linked on to any of the English thegns who retained their estates. The Coplestones held chief place of the three, and were called the ' Great Coplestones,' and ' Coplestones of the White Spur,' having, according to Westcote, the special grant of a silver collar, or chain of SS., and of silver spurs. The origin of the name Copelanstan is doubtful ; but very likely it is the 'headland ' or 'the chief stone.' " 
Records show Hugh of Coplestone in the year 1275 was Lord of the Manor at that time. He held a hamlet and manor in the parish of Colebrook. Conjecturally, one branch of the family may be descended from the tenant of the parish, Manfred, who held it from William Cheever at the time of the taking of the Domesday Book by Duke William of Normandy in 1086. (This Guillaume La Chievre of Normandy, held 47 baronies in the county of Devon, and held a family seat at Bradninch in Devon. He attended William the Conqueror at Hastings in 1066,) Manfred was most likely a son or nephew of this great Baron Guillaume.
In nearby Cornwall, another early branch of the family was found. "Another manor called Biscovey, was anciently in the family of Coplestone. This, in the year 1563, was sold by one of that family residing at Warlegh, in Devonshire, to Mr. Richard Trehawke, of St. Blazey." 
The manor of Lametton in the parish of St. Keyne, Cornwall was another ancient family seat of the family. "In this family it probably remained until the fourth of Elizabeth, when thirteen manors were sold in this county, to procure for John Coplestone, Esq. the royal pardon, he having forfeited his life to the laws of his country."