It appears that about the year 1240 Gilbert Marshal, Earl of Pembroke, assisted William St. Maur to wrest a place called Woundy (now Undy), near Caldicot in Monmouthshire, from the Welsh.

The eldest son of this marriage was Sir William St. Maur (d. 1390), or Seymour (the modernised form of the name appears to have come into use about this date), who was an attendant on the Black Prince, and who died in his mother's lifetime, leaving a son Roger St Maur (c. 1366-1420), who inherited his grandmother's estates and added to them by his marriage with Maud Esturmy, daughter of Sir William Esturmy (died 1427) of Wolf Hall, Wiltshire.

They increased their boundaries by fortunate alliances with heiresses, and the head of the family married into a collateral branch of the lordly line of Beauchamp.

Although the royal kindred appears somewhat doubtful, yet it is undeniable that the sovereign of England gained by this alliance one brother in-law who bore the name of Smith, and another whose grandfather was a blacksmith at Putney.

He took an active part in suppressing the Cornish Rebellion of 1497; and afterwards attended Henry at the Field of the Cloth of Gold, and on the occasion of the emperor Charles V's visit to England in 1522.

The Protector was married twice; and, probably owing to the adultery of his first wife whom he repudiated about 1535, his titles and estates were entailed first on the issue of his second marriage with Anne, daughter of Sir Edward Stanhope.

In 1672 he was elected speaker, an office which he filled with distinction until 1679, when, having been unanimously re-elected to the chair, the king refused to confirm the choice of the Commons.

On the accession of James II, Seymour courageously opposed the arbitrary measures of the Crown; and at the revolution he adhered to the Prince of Orange.

The eldest son of the Protector's second marriage, Edward Seymour (1537–1621), was relieved by act of parliament in the reign of Queen Mary from the attainder passed on his father in 1551, and was created Baron Beauchamp and earl of Hertford in 1559.

The eldest of these sons was Edward Seymour (1561–1612), styled Lord Beauchamp notwithstanding the question as to his legitimacy, who in 1608 obtained a patent declaring that, after his father's death he should become earl of Hertford.

He, however, died before his father, leaving three sons, one of whom, William, became 2nd duke of Somerset; and another, Francis, was created Baron Seymour of Trowbridge in 1641.

When, however, the popular party proceeded to more extreme measures, Francis Seymour refused his support, and was rewarded by being raised to the peerage; he voted in the House of Lords against the attainder of Strafford, and in 1642 he joined Charles at York and fought on the royalist side throughout the Great Rebellion.

Henry Seymour (1729–1805), a son of the 8th duke of Somerset's brother Francis, was elected to the House of Commons in 1763; in 1778 he went to France, and fixing his residence at Prunay, near Versailles, he became the lover of Madame du Barry, many of whose letters to him are preserved in Paris.

His son Sir George Francis Seymour (1787–1870), admiral of the fleet, began his naval career by serving under Nelson; in 1818 he became Sergeant-at-arms in the House of Lords, a post which he retained till 1841, when he was promoted to the rank of rear-admiral and appointed a lord of the admiralty; his eldest son, Francis George Hugh Seymour (1812–1884), succeeded his cousin Richard Seymour-Conway as 5th marquess of Hertford in 1870.

He lost an arm in Howe's action on 1 June 1794; and between 1796 and 1810 as commander of the Spitfire, and afterwards of the Amethyst, he captured a great number of prizes from the French in the English Channel.

Wilhelmina, Duchess of Cleveland (1819–1901), in her 1889 work The Battle Abbey Roll with some Account of the Norman Lineages wrote about the Esturmy family, which held the estates of Tottenham, Wulfhall and the Savernake Forest.

He married Joan Crawthorne, the widow of Sir John Beaumont of Shirwell and Saunton in North Devon, by whom he had no male progeny, only two daughters and co-heiresses including Maud Esturmy, wife of Roger II Seymour (c.1367/70-1420),[4] feudal barony of Hatch Beauchamp in Somerset, by whom she had a son John Seymour (died 1464).

The Seymour family (anciently de St. Maur) is earliest recorded seated at Penhow Castle in Glamorgan in the 12th century.

[8] Thomas Gerard in his "Description of Somerset" (1633) wrote as follows:[9] The Duke was executed in 1552 for felony on the order of his nephew King Edward VI, and was attainted by Parliament shortly thereafter when all his titles were forfeited.

It was probably Edward Seymour, 1st Earl of Hertford (1539–1621), son and heir of the 1st Duke, of nearby Wulfhall, who in about 1575 built the first Tottenham House, then known as Totnam Lodge, and enclosed its surrounding land to form a deer park.

[10] The Seymours were hereditary Wardens of Savernake Forest, which office together with most of their Wiltshire estates had been inherited by marriage to the daughter and heiress of Sir William Esturmy (died 1427), of Wulfhall.

[11] William Seymour, 2nd Duke of Somerset (1587–1660), grandson, inherited the estates on the death of his grandfather the 1st Earl, his father having predeceased the latter.

Elizabeth Seymour's son and heir was Charles Bruce, 3rd Earl of Ailesbury (died 1747), of Houghton House in the parish of Maulden, in Bedfordshire, who in 1721 rebuilt Totnam Lodge to the design of his brother-in-law the pioneering Palladian architect Lord Burlington.