 = Henry of Grosmont , 1st Duke of Lancaster = 
 
 Henry of Grosmont , 1st Duke of Lancaster , 4th Earl of Leicester and Lancaster , KG ( c . <unk> – 23 March <unk> ) , also Earl of Derby , was a member of the English nobility in the 14th century , and a prominent English diplomat , politician , and soldier . The son and heir of Henry , 3rd Earl of Lancaster , and Maud <unk> , he became one of Edward III 's most trusted captains in the early phases of the Hundred Years ' War and distinguished himself with victory in the Battle of <unk> . He was a founding member and the second Knight of the Order of the Garter in <unk> , and in 1351 was created duke . Grosmont was also the author of the book <unk> de <unk> medicines , a highly personal devotional treatise . He is remembered as one of the founders and early patrons of Corpus Christi College , Cambridge , which was established by two of the <unk> of the town in <unk> . 
 
 = = Family background and early life = = 
 
 Grosmont 's uncle , Thomas of Lancaster , was the son and heir of Edward I 's brother Edmund <unk> . Through his inheritance and a fortunate marriage , Thomas became the wealthiest peer in England , but constant quarrels with King Edward II led to his execution in <unk> . Having no heir , Thomas 's possessions and titles went to his younger brother Henry – Grosmont 's father . Earl Henry of Lancaster <unk> to the deposition of Edward II in <unk> , but did not long stay in favour with the regency of Queen Isabella and Roger Mortimer . When Edward III took personal control of the government in 1330 , relations with the Crown improved , but by this time the older Henry was already struggling with poor health and blindness . 
 Little is known of Grosmont 's early years , but that he was born at Grosmont Castle in Grosmont , Monmouthshire , Wales , and that he was born c . <unk> , not around the turn of the century as previously held . According to his own memoirs , he was better at martial arts than at academic subjects , and did not learn to read until later in life . In 1330 he was knighted , and represented his father in parliament . The next year he is recorded as participating in a royal tournament at <unk> . 
 In <unk> he took part in Edward 's Scottish campaign , though it is unclear whether he was present at the great English victory at the Battle of <unk> Hill . After further service in the north , he was appointed the King 's lieutenant in Scotland in 1336 . The next year he was one of the six men Edward III promoted to the higher levels of the peerage . One of his father 's lesser titles , that of Earl of Derby , was bestowed upon Grosmont . 
 
 = = Service in France = = 
 
 With the outbreak of the Hundred Years ' War in <unk> , Grosmont 's attention was turned towards France . He took part in several diplomatic missions and minor campaigns and was present at the great English victory in the naval Battle of <unk> in <unk> . Later the same year , he was required to commit himself as hostage in the Low Countries for the king 's considerable debts . He remained hostage until the next year and had to pay a large ransom for his own release . On his return he was made the king 's lieutenant in the north and stayed at <unk> until <unk> . The next years he spent in diplomatic negotiations in the Low Countries , Castile and Avignon . 
 In 1345 Edward III was planning a major assault on France . A three @-@ <unk> attack would have the Earl of Northampton attacking from Brittany , the king himself from Flanders , while Grosmont was dispatched to <unk> to prepare a campaign in the south . Moving rapidly through the country , he confronted the Comte d ’ Isle at <unk> on 21 October and there achieved a victory described as " the greatest single achievement of Lancaster 's entire military career " . The ransom from the prisoners has been estimated at £ 50 @,@ 000 . The next year , while Edward was carrying out his <unk> campaign , Grosmont laid siege to , and captured , <unk> , before returning home to England in <unk> . 
 
 = = Duke of Lancaster = = 
 
 In 1345 , while Grosmont was in France , his father died . The younger Henry was now Earl of Lancaster – the wealthiest and most powerful peer of the realm . After participating in the Siege of Calais in <unk> , the king honoured Lancaster by including him as a founding knight of the Order of the Garter in <unk> . A few years later , in 1351 , Edward bestowed an even greater honour on Lancaster when he created him Duke of Lancaster . The title of duke was of relatively new origin in England ; only one other <unk> title existed previously . 
 In addition to this , Lancaster was given palatinate status for the county of Lancashire , which entailed a separate administration independent of the crown . This grant was quite exceptional in English history ; only two other counties <unk> existed : Durham , which was an ancient ecclesiastical palatinate , and Chester , which was crown property . 
 It is a sign of Edward 's high regard for Lancaster that he would bestow such extensive privileges on him . The two men were second cousins through their great @-@ grandfather Henry III and practically <unk> ( Edward was born in <unk> ) , so it is natural to assume that a strong sense of <unk> existed between them . Another factor that might have influenced the king 's decision was the fact that Henry had no male heir , so the grant was made for the Earl 's lifetime only , and not intended to be hereditary . 
 
 = = = Further prestige = = = 
 
 Lancaster spent the <unk> intermittently campaigning and negotiating peace treaties with the French . In <unk> he was present at the naval victory at <unk> , where he allegedly saved the lives of the Black Prince and John of Gaunt . The years 1351 @-@ 2 he spent on crusade in Prussia . It was here that a quarrel with Otto , Duke of Brunswick , almost led to a duel between the two men , narrowly averted by the intervention of the French king , John II . In the later half of the decade campaigning in France resumed . After a <unk> in Normandy in <unk> and the siege of Rennes in <unk> , Lancaster participated in the last great offensive of the first phase of the Hundred Years ' War : the <unk> campaign of <unk> @-@ 60 . Then he was appointed principal <unk> for the Treaty of <unk> , where the English achieved very favourable terms . 
 After returning to England in November <unk> , he fell ill early the next year , and died at Leicester Castle on 23 March . It is likely that the cause of death was the plague , which that year was making a second visitation of England . He was buried in the Church of the <unk> of Our Lady of the <unk> , Leicester , the church which he had built within the religious and charitable institution founded by his father next to Leicester Castle , and where he had re @-@ buried his father some years previously . 
 
 = = Private life = = 
 
 Lancaster was married to Isabella , daughter of Henry , Lord Beaumont , in 1330 . The two had no sons , but two daughters : Maud and Blanche . While Maud was married to William I , Duke of <unk> , Blanche married Edward III 's son John of Gaunt . Gaunt ended up <unk> Lancaster 's possessions and <unk> title , but it was not until <unk> , when the dying King Edward III was largely incapacitated , that he was able to restore the palatinate rights for the county of Lancaster . When Gaunt 's son Henry of <unk> <unk> the crown in <unk> and became Henry IV , the vast Lancaster inheritance , including the Lordship of <unk> , was merged with the crown as the Duchy of Lancaster . 
 We know more about Lancaster 's character than of most of his contemporaries through his memoirs , the <unk> de <unk> medicines ( Book of the Holy Doctors ) . This book is a highly personal treatise on matters of religion and piety , but it also contains details of historical interest . It , among other things , revealed that Lancaster , at the age of 44 when he wrote the book in <unk> , suffered from <unk> . The book is primarily a devotional work though ; it is organized around seven wounds which Henry claims to have , representing the seven sins . Lancaster confesses to his sins , explains various real and mythical medical <unk> in terms of their theological symbolism , and <unk> the reader to greater morality . 
 
 = = <unk> = = 
 
 
 