Robert “de Mosters”was a tenant of Earl Alan’s in Yorkshire 1086, and also held Truswell in Notts, part of the great Richmond Fee. “There are three places called ‘Les Moutiers,’ ‘Monasteria,’ in the department of Calvados in Normandy; but if he were a Brefon, as seems probable, Moutiers near La Guerche may be the more likely place for him to have come from. Robert, however, was no doubt a near relation of ‘Lisois de Monasteriis,’ a brave knight in the Conqueror’s army in the Northern campaign of 1069, who, when the river Aire had stopped their progress for three weeks, sought for a ford both above and below, and at last with great difficulty discovered one, by which he crossed over at the head of sixty bold men-at-arms, and though assailed by the enemy with great force stoutly held his ground. Next day Lisois returned and announced his discovery, and the army passed over without further delay (Ordericus IV. 5). Nothing more is recorded of Lisois, and if he had been surviving or had left sons living at the time of the ‘Survey’ we should have expected to find that he had been amply rewarded for his signal exploit, which was probably only one of his martial achievements. Robert, therefore, was rather a brother, as Gale thought, than a son of Lisois; but he left a son named after him, Lisois, who died without issue, though he succeeded his father, and owed, in 1131, ₤24, a mark of silver and saddle-horse, for his relief (Pipe Roll). Robert, however, left another son, Galfrid, father of Robert de Monasteriis, to whom Earl Alan confirmed by charter the lands held by Galfrid his father, Liserus his uncle (patruus), and Robert his grandfather (Gale’s Honor of Richmond, p. 101). Descendants in the male line remain to this day in Notts; and the Manor of Kirklington (held in Domesday) belongs to one of the family of the Earl”(Marquess?) “of Ormonde, who himself represents Robert de Musters through the Wandesfords.” - A. S. Ellis.

According to Thoroton, Truswell or Tireswell was held by seven generations of Robert’s descendants. Lisiardus de Monasterio, and Gundra his sister, occur in the county 1194-99 (Rotuli Curiae Regis): and Robert, in 1279, held two fees “pro Warda Castri de Richmond.” - Gale's Richmonds hire. The last heir, Robert’s great-grandson, Sir Henry, “by his second wife Elizabeth, daughter of Sir Brian Thornton, had an only daughter and heir named Elizabeth, who was first married to Alexander de Moubray, and after his death to John de Wandesford of Westwick in Yorkshire, by whom she had a son and heir called John de Wandesford of Kirtlington in that county, born about 45 Ed. III.: of whom there is a family still remaining, but by her husband Moubray she had a daughter and heir Elizabeth, the first wife of Sir William Gascoyne the chief judge.” - Thoroton's Notts.

Yet the old name was not lost, and still lives in the county. Colwick, the present seat of the family, was acquired by a Sir John Musters who died in 1689: won, it is said, at cards from one of the Byrons. Thoroton, however, gives a different account. “Sir John Byron,” he tells us, “sold the manor to Sir James Stonehouse, being of a very great yearly value, but never got much above half the money, by reason of the breaking out of the war, wherein it was stop’d by the rebells, but since the return of the king, Richard, the present Lord Byron, hath accepted of some small part, and confirmed the title of Sir John, the present owner.” Mundy Musters, third in descent from Sir John, was High Sheriff of Notts in 1753, as was his son John in 1777. John’s son married Mary Anne Chaworth, the “bright morning star of Annesley,” who had been Lord Byron’s early love.