“SIR ROBERT DE TREGOZE, second son, was, though such, the great man of the family, and founded its most important branch; and this because he acquired immense wealth by his marriage. He took to wife Sibilla, daughter and heiress of Robert de Ewyas, Lord Ewyas, of Harold Ewyas, in Herefordshire; and in 9th Ric. I. (Easter Term) had a suit with Hermenus de Braton for the advowson of Braton church in Norfolk, part of her vast inheritance. But it appears, that though duly married, a strange contest arose in the 11th John regarding her; when, in Easter Term, William de Newmarket was summoned to show by what right be claimed to wife her who was Robert Tregoz's wife ; for it appears that Richard I had given her to Tregoz in marriage. Whereupon Newmarket came and said that he had married her in the time of Richard the First by gift of Robert de Ewyas her father. It is very certain, however, that Tregoz had sufficient power to retain the heiress; for in 13th John, Michaelmas Term, we find "Robert de Tregoze and Sibilla his wife" impleading Ralph de St. Maur for land in Bren, in Somersetshire, the right of the said Sibilla and in Trin. Term, 14th John, they had recovered the said lands against St. Maur.
This Sibilla de Ewyas brought immense domains, including the castle of Ewyas Harold in Herefordshire, into the Tregoze family.

Meanwhile Sir Robert de Tregoze was High Sheriff of Wilts 3rd Ric. I.; and in three years after was engaged in the expedition made into Normandy. In Ist John (1200), he gave the King 200 marks in silver to have granted to him the wardship of  the heir and lands of Geoffry Hose; and in 7th John (1206), on collecting the scutage of that King's reign, answered thirty eight marks for nineteen knight's fees belonging to the honour of Robert de Ewyas his father in law. He also held one knight's fee in Irchingfield ; but died about the year 1212.

Sibilla, his wife, survived him, and in 1214 married, secondly, Roger de Clifford, for which marriage that nobleman gave the King 1000?. Roger de Clifford died 1231-2, in the lifetime of his elder brother Walter de Clifford, having had by the said Sibilla a son, Roger de Clifford, a Baron famous for his extraordinary experience in military affairs, ancestor of the Lords de Clifrord. Sibilla herself was dead in 1236, and by Tregoze, her former husband, had two sons and a daughter.
[The Topographer and Genealogist, Volume II, 1853]”