The original William de Mohun was a Norman warlord from the town of Moyon near St. Lô in western Normandy, who may or may not have been present at the battle of Hastings. He was certainly later the Sheriff of Somerset at the time of the compilation of the Domesday Book when he was also recorded as holding fifty-four manors in Somerset, eleven in Dorset, and one each in Devon and Wiltshire as tenant in chief. It was his son, also known as William de Mohun, who later became a supporter of the Empress Matilda, and sometime in the period between April and June 1141 she created him an earl. According to the foundation charter of Burton Abbey he was 'Willelmus de Moyon, comes Somersetensis', although the Gesta Stephani claims that he was created the Earl of Dorset. However since it is known that Dorset was one of the four counties to which Matilda gave Aubrey de Vere as the choice for his earldom in the following year, this seems to be an error, likely caused by the fact both counties were under the jurisdiction of a single sheriff.

Of course his title was not recognised by king Stephen and since Henry II did not grant him a charter, William's title is regarded as having lapsed with his death, which occurred certainly before 1155 and probably sometime around the year 1145. He did however leave a son named William who succeeded to his considerable estates and was the ancestor of the later Barons Mohun. (For which see Baron Mohun.)


John of Gaunt, the Duke of Lancaster and third son of king Edward III had a long standing mistress by the name of Katherine Roet by whom he had three illegitimate sons. In 1396 John of Gaunt later married thisKatherine Roet and these sons were legitimised by an Act of Parliament in 1397, although Henry IV later issued letters patent that purported to limit this "for all purposes save succession to the crown".

The eldest of these sons was John de Beaufort, who was created Earl of Somerset by Richard II on the 10th February 1397. He was further created the Marquess of Somerset on the 9th September 1397 and Marquess of Dorset on the 29 September 1397 but was stripped of these two later titles by Henry IV shortly after his assumption of the throne on the 3rd November 1399. Some of his supporters later petioned the throne to have these marquessates restored but John was not keen on the idea, being of the opinion that "the name of marquess is a strange name in this realm".

John de Beaufort was succeeded by his oldest son Henry Beaufort who died unmarried in 1418. His younger brother John followed, who was also later created Earl of Kendal and Duke of Somerset on the 28th August 1443, but died less than a year later on the 27th May 1444. John Beaufort left no sons, only daughters, amongst whom was Margaret Beaufort, who married Edmund Tudor, the Earl of Richmond and had issue in the form of Henry Tudor, later Henry VII. With no male heirs the titles of Duke of Somerset and Earl of Kendal became extinct, but the title of Earl of Somerset was inherited by his younger brother Edmund Beaufort.

Edmund who had already been created Earl of Dorset in 1441 and Marquess of Dorset in 1443 therefore became the 4th Earl in 1444. Four years later on the 31st March 1448 he was granted the title Duke of Somerset and thereby became the 1st Duke of the second Beaufort creation. He was latter killed at the battle of St. Albans in 1455.

He was succeeded by his son Henry Beaufort who became one of the leading Lancastrian leaders who fought at the both the battle of Wakefield in 1460 and the second battle of St Albans in 1461. But he fled to Scotland after the defeat at Towton in the same year. He returned to fight with the Lancastrian army at the battle of Hexham in 1464 when he was captured and executed by John Neville later Earl of Northumberland.

Henry died without legitimate issue, (although he did have an illegitimate son named Charles Somerset, who became the Earl of Worcester), and he was therefore succeeded by his brother Edmund. However the victorious Yorkists passed an act of parliament to strip Henry of his titles as Duke of Somerset and Marquess of Dorset. Despite this his brother Edmund continued to be styled as Duke of Somerset by the Lancastrians and is therefore generally listed as the 3rd Duke. (Although not apparently as the 3rd Marquess of Dorset, a title that seems to have died with Henry). In any event, Edmund Beaufort duke or not, fought at the battle of Tewkesbury after which he fled to the sanctuary of Tewkesbury Abbey, but was discovered, removed and executed, once again by Edward IV. He was the last of the legitimate male descendants of John de Beaufort and his various titles became extinct.


Robert Carr was a Scotsman who came south with the court of James VI of Scotland when he became James I of England. Robert became one of the king's favourites and rewarded with, amongst other things, the titles of Viscount Rochester in 1611 and that of Earl of Somerset in 1613. In 1616 both he and his wife were convicted of the murder of his former friend, Sir Thomas Overbury; although later both were pardoned they were not released until 1622. Robert died without heirs in 1645 at which time his titles became extinct. (See the Thomas Overbury affair for further details of Robert's fall from grace.)

Note on the succession of the Beaufort Dukes

There were two separate creations of the title Duke of Somerset in the Beaufort family in 1443 and in 1448 and therefore Edmund Beaufort is properly the 1st Duke of the 1448 creation, since in no shape or form can he, as a younger brother of the John Beaufort of the 1443 creation, be regarded as continuing that older creation. Be aware that not everyone follows this convention and some sources list Edmund Beaufort as the 2nd Duke of Somerset, with the succeeding Beaufort Dukes similarly renumbered.

(including the Beaufort Dukes of Somerset)



Earl of Somerset created 10th February 1397

The 1st Earl was also Marquess Of Somerset between 1397 and 1399.

Duke of Somerset created 28th August 1443

Earl of Somerset continuation of 1397 creation

Duke of Somerset created 31st March 1448



  • The 1911 Encyclopedia Brittanica entry for SOMERSET, EARLS AND DUKES OF See
  • John of Gaunt at
  • The Columbia Encyclopedia, Sixth Edition.(2001)entry for Somerset, Robert Carr, earl of See
  • Royal Genealogy information held at University of Hull see
  • RoyaList Online at
  • Charles Arnold Baker The Companion to British History (Longcross Press, 1996)
  • THE ENGLISH PEERAGE or, a view of the ANCIENT and PRESENT STATE of the ENGLISH NOBILITY London: (1790) see