At present we are unable to find information about Count Robert earlier than after the Norman Conquest, He became The lord of the manor of Whitesand, and William invested in him with more than two thirds of Cornwall, so that, though he never assumed the title, he was in fact the first earl of Cornwall. Not content with these estates-he became the greatest landowner in England next to the King, with eight hundred manors in twenty counties.
1066- At the time of the conquest St Allen in Cornwall was part of the great Manor of Cargoll. The capital of the Manor was in Newlyn, and the Manor also covered parts of the parishes of Crantock and St Erme. It was originally the property of the monks of St Petroc at Bodmin, and was seized by Count Robert of Mortain. He presented it to one of his Barons, Reginald de Valle Torta, Lord of Trematon Castle. The ruins of Trematon Castle are seen from the train on the north side of the line between St.Germans and Saltash.
1086-The first mention of an existence of a castle at Launceston Cornwall occurs in the Domesday Survey. It records the Earl Robert of Mortain holds the castle of Dunhevet, he had been rewarded the huge Earldom of Cornwall as reward for his efforts in helping William to conquer England.
He appears to have chosen Launceston or Dunheved as the administrative centre of his domain, which had a lasting effect on the importance of the town in the local government of Cornwall.
Alternon Cornwall the supposed Penponta of the Doomsday Book Survey was also granted to Robert, by William the Conqueror.
1090- Robert died having rebelled against William Rufus at Pevensey. He was succeeded by his son William.