Duke of Somerset, from the county of Somerset, is a hereditary title that has been created five times in the Peerage of England. It is particularly associated with two families: the Beauforts, who held the title from the creation of 1448, and the Seymours, from the creation of 1547, in whose name the title is still held. The present dukedom is unique, in that the first holder of the title created it for himself in his capacity of Lord Protector of the Kingdom of England, using a power granted in the will of his brother in law King Henry VIII.

The only subsidiary title of the current duke of Somerset is Baron Seymour of Trowbridge, which is used as a courtesy title by the eldest son and heir of the duke. This courtesy title is the lowest in rank of all heirs to dukedoms in the peerages of the British Isles, yet the holder's precedence is higher than his title suggests, by virtue of the seniority of the Dukedom of Somerset (the only more senior non-royal duke is the Duke of Norfolk).

Several other titles have been held by the dukes of Somerset, but have become extinct. These include: Earl of Kendal (created 1443, extinct 1444 but later recreated in France) Earl of Somerset (created 1397, forfeit 1461) Marquess of Dorset (1st creation 1397, degraded 1399; 2nd creation 1442, forfeit 1461) Marquess of Somerset (created 1397, degraded 1399) Earl of Dorset (3rd creation 1442, forfeit 1461) Viscount Rochester (created 1611, extinct 1645) Viscount Beauchamp of Hache (created 1536, forfeit 1552) Earl of Hertford (created 1537, forfeit 1552; and created 1559, extinct 1750) Marquess of Hertford (created 1640, extinct 1675) Baron Seymour of Trowbridge (created 1641, became a subsidiary title 1675, extinct 1750) Baron Percy (4th creation 1722, separated 1750) Earl of Egremont and Baron Cockermouth (created 1749, separated 1750) Earl St. Maur (created 1863, extinct 1885).

Estates and residences The ducal seat is Bradley House in Maiden Bradley, west Wiltshire, with a secondary estate at Berry Pomeroy Castle, Totnes, Devon. The principal burial place for the Seymour family today is All Saints' Church, Maiden Bradley, adjacent to Bradley House; the church and the family cemetery can be reached from the grounds of Bradley House via private access.The grave of Algernon Seymour, 15th Duke of Somerset, 19 July 2013

In the 1883 edition of John Bateman's The Great Landowners of Great Britain and Ireland, Edward St Maur, 12th Duke of Somerset's estates were recorded as spanning 25,387 acres across England, including 8,138 acres in Devon, 6,553 acres in Somerset, 5,824 acres in Wiltshire, 2,865 acres in Lincolnshire, 1,640 acres in Buckinghamshire, 289 acres in Cambridgeshire, 32 acres in Norfolk, and 46 acres in Dorset, which produced a combined annual income of £37,577.

Previous residences Former country seats occupied by the family include Bulstrode Park in Buckinghamshire, which was purchased from William Bentinck, 4th Duke of Portland by Edward St Maur, 11th Duke of Somerset in 1811. His son Edward Seymour, 12th Duke of Somerset commissioned the present mansion, which was completed in 1865. After the 12th Duke's death in 1885 the Dukedom passed to his younger brother Archibald St Maur, 13th Duke of Somerset, whilst the Bulstrode estate passed to 12th Duke's youngest daughter, Lady Helen Ramsden, and then to her son, Sir John Frecheville Ramsden and his descendants.

London residences Somerset House, The Strand The first member of the Seymour family to hold the Dukedom of Somerset, Edward Seymour, 1st Duke of Somerset commenced construction of Somerset House on The Strand in central London in 1549; however he was attainted for Treason and executed in 1552, prior to the completion of the house. Although the former Tudor mansion (also known as Somerset Place and Old Somerset House) and the current Georgian building complex on this site have retained the name Somerset House, none of the subsequent Dukes of Somerset have resided at this Somerset House.

Somerset House, 40 Park Lane In 1808 Edward St Maur, 11th Duke of Somerset purchased the lease of No. 40 Park Lane, Mayfair from Neil Primrose, 3rd Earl of Rosebery, and the house continued to be known as Somerset House, Park Lane until its demolition in 1915, although the freehold of the property was held by the Grosvenor Family. The 11th Duke maintained 40 Park Lane as his London residence until his death in 1855, after which the house was occupied by his widowed second wife Margaret, Duchess of Somerset until her own death in 1880. By April 1881 the 11th Duke's son Edward St Maur, 12th Duke of Somerset had moved into No. 40 Park Lane, which was his London home until he died in 1885. As the 12th Duke had been predeceased by his two sons Ferdinand, Earl of St Maur and Lord Edward Seymour, his successor to the Dukedom was his brother Lord Archibald Seymour. The lease of Somerset House, Park Lane was bequeathed by the 12th Duke to his eldest daughter Lady Hermione Graham (wife of Sir Frederick Graham, 3rd Baronet), who later sold the lease in 1890.

28 Berkeley Square The 13th Duke's London House was No. 28 Berkeley Square from c. 1887, until his death in 1891. after which his leasehold of the property was inherited by his brother Algernon St Maur, 14th Duke of Somerset. The 14th Duke died in 1894 and was succeeded by his oldest son Algernon St Maur, 15th Duke of Somerset; the lease of 28 Berkeley Square passed to the 14th Duke's second son Lord Percy St Maur, and was used as a London house by Lord Percy and his mother Horatia, Dowager Duchess of Somerset. Lord Percy died in 1907, and the leasehold of 28 Berkeley Square then passed to the 14th Duke's third son Lord Ernest St Maur, who relinquished the lease in 1920.

Grosvenor Square Algernon St Maur, 15th Duke of Somerset took a long lease of No. 35 Grosvenor Square, Mayfair in 1898. Following his death in 1923 he was succeeded as Duke of Somerset by his third-cousin-once-removed Edward Seymour, 16th Duke of Somerset. The 15th Duke bequeathed his lease of 35 Grosvenor Square and a life annuity of £4,000 to his widow Susan, Duchess of Somerset, and she continued to live at 35 Grosvenor Square until early 1934, after which she leased No. 30 Grosvenor Square until her death in 1936.

Creation of Empress Matilda William de Mohun of Dunster (?–), a favourite of Empress Matilda and a loyal supporter of her in the war against King Stephen (during which he earned the epithet of the "Scourge of the West"), was given the title Earl of Somerset in 1141. In the foundation charter of the priory at Bruton he describes himself as "Willielmus de Moyne, comes Somersetensis". The title was not recognised by Stephen or Henry II (Matilda's son), and his descendants did not use it.

Beaufort creations

John Beaufort (1371/1373–1410) was the eldest son from John of Gaunt's marriage to Katherine Swynford. He was created Earl of Somerset on 10 February 1397; on 9 September 1397, following his marriage to Margaret Holland, daughter of Thomas Holland, 2nd Earl of Kent, he was promoted to Marquess of Somerset, and a few weeks later on 29 September 1397 he was created also Marquess of Dorset. However, in 1399, when Henry IV came to the throne, his two marquessates were revoked.

The Commons petitioned the King for his restoration, but Somerset himself objected, stating "the name of marquess is a strange name in this realm". He was succeeded as Earl of Somerset by his son Henry Beaufort (1401–1418), but his early death left the earldom to his brother John Beaufort (1404–1444). He was created Duke of Somerset and Earl of Kendal on 28 August 1443 and died less than a year later on 27 May 1444, perhaps by suicide. The Dukedom of Somerset and Earldom of Kendal became extinct.

The Earldom of Somerset passed to his brother Edmund Beaufort, Count of Mortain (–1455). Edmund had been created Earl of Dorset on 18 August 1442 and Marquess of Dorset on 24 June 1443. He was created Duke of Somerset under a new creation on 31 March 1448. Despite this, he is usually referred to as the 2nd Duke of Somerset.

The second duke was killed at the First Battle of St Albans on 22 May 1455 and his peerages passed to his son Henry Beaufort (1436–1464) who had been known as the Earl of Dorset since his father's creation as Duke of Somerset. After the defeat at the battle of Towton on 29 March 1461 he fled to Scotland and was attainted on 4 November 1461. All his honours and estates were declared forfeit. His titles were restored to him on 10 March 1463 but he deserted the king and was captured and beheaded after the battle of Hexham on 15 May 1464.

He was unmarried, but his illegitimate son Charles Somerset became the 1st Earl of Worcester. Henry's titles were forfeited by act of Parliament; but his brother Edmund Beaufort (–1471) was styled Duke of Somerset by the Lancastrians.Jonathan Hughes, "Somerset, Charles, first earl of Worcester (c.1460–1526)", Oxford Dictionary of National Biography, Oxford University Press, September 2004; online edition, January 2007 [accessed 1 Sept 2010] (Subscription required for online version) After the Battle of Tewkesbury on 4 May 1471 he fled and took refuge in Tewkesbury Abbey. He was beheaded by the Yorkists, and buried in the abbey church. Upon his death the house of Beaufort became extinct in the legitimate line.

Tudor creations In 1499 Henry VII nominated his infant son Edmund Tudor to the dukedom of Somerset at his baptism, but the child, just over a year old when he died, was probably never formally created a peer.

The illegitimate son of Henry VIII, Henry FitzRoy (1519–1536), by Elizabeth Blount, was created Earl of Nottingham, and Duke of Richmond and Somerset on 18 June 1525. He died without heirs on 23 July 1536, when his peerages became extinct.

Earl of Somerset under James VI and I Robert Carr (–1645), born Kerr/Ker, son of Sir Thomas Ker of Ferniehirst, became a favourite of King James VI and I. On 25 March 1611 he was created Viscount Rochester, and subsequently a privy councillor. On the death of Lord Salisbury in 1612 he began to act as the king's secretary. On 3 November 1613 he was created Earl of Somerset.David M. Bergeron, Royal Family, Royal Lovers (University of Missouri, 1991), p. 87. He died in July 1645, leaving a daughter, Anne. His titles became extinct.

Seymour creation and 17th century claim to revert to Beaufort creations

Edward Seymour, 1st Duke of Somerset (–1552), was the eldest brother of Jane Seymour, the third wife of King Henry VIII, and was thus an uncle of King Edward VI. Henry had created him Viscount Beauchamp "of Hache" in 1536, at the time of the marriage, and Earl of Hertford in 1537. On the death of Henry VIII on 28 January 1547, Seymour was named in the King's will as one of his sixteen executors who then formed a regency council to rule during the minority of his nine-year-old son and successor King Edward VI. Seymour was elected head of the council, which on 1 February 1547 appointed him as "Lord Protector of the Realm and Governor of the King's Person", when he became "the most powerful man in England, a king in all but name" and ruled by proclamation.Sarah Bryson, "Edward Seymour, Duke of Somerset", www.tudorsociety.com