Four bastard children of John of Gaunt and his mistress Katherine Swynford vigorously made their way in the world despite their questionable origin, and when all four were retrospectively declared legitimate they were each set on course for advancement.Following the coup in 1399 when their half-brother became King Henry IV, the Beauforts were placed at the centre of government, and for three generations they served the Lancastrian monarchy in its grandiose ambitions, and in its decline to eventual extinction. John Brunton discusses how the Beauforts took much of the blame for losing first the Hundred Years War for the English and then the Wars of the Roses for the Lancastrians.However, the account also shows the earls and dukes of Somerset and their families acted as a constant, a stabilising influence in the uncertain times of the fifteenth century.