Today marks the 698th anniversary of the birth of King Edward III at Windsor Castle on Monday 13 November 1312, or as his contemporaries would put it, 'on the feast of St Brice in the sixth year of the reign of our lord King Edward, second of that name after the Conquest', or 'on the Monday after St Martin in the sixth year of the reign of our lord King Edward, son of King Edward'.
Edward of Windsor's father Edward II was then twenty-eight and his mother Isabella of France probably seventeen, or shortly to turn seventeen. Edward was born as heir to the English throne, displacing his father's twelve-year-old half-brother Thomas of Brotherton (whom the king made earl of Norfolk a few weeks later), and would grow up to be, apart from his younger brother John of Eltham, the only surviving grandson of Philip IV of France. He was destined to live until the age of sixty-four, father twelve legitimate children and at least three illegitimate ones, succeed to his father's throne while his father was still alive, begin the Hundred Years War with France and live through three outbreaks of the Black Death; to say that his life was eventful and exciting barely begins to describe it.
As was so often the case in Edward II's reign, little Edward was born at a time when his father was feuding with his barons and the kingdom was teetering on the brink of civil war, thanks to the killing of the king's beloved Piers Gaveston five months earlier (and let me reiterate here that Isabella was already pregnant at the time of Piers' death, and that Edward II's relationship with Piers therefore did not impede his marital relations with his queen, as a lot of people seem to think). Edward II spent the summer of 1312 provisioning his castles, summoning loyal barons to him and ordering London to close its gates against Piers' killers, having left Isabella in the north of England, presumably for her own safety. The king did find time, though, to pay a man called John de Colon of Lombardy "for making his minstrelsy with snakes in the presence of the king" at Canterbury on 16 August. 
The king and queen were reunited on or around 9 September 1312 for the first time since late June, and by the 17th of that month had retired to Windsor Castle, where they would spend most of the next few months together. They were accompanied by the dowager queen Marguerite, Edward's stepmother and Isabella's aunt, and Marguerite's brother Louis, count of Evreux, whom their half-brother Philip IV had sent to England to negotiate between the king and his barons in the aftermath of Piers Gaveston's murder. Evreux had long been on close terms with Edward, and it was to him that Edward sent his humorous letter about lazy dogs and big trotting palfreys in 1305.
Edward II gave two pounds to a Welsh minstrel called Coghin, who performed for him, and presumably the eight-months-pregnant Isabella, at Windsor on 12 October.  A few days later, Edward granted his wife permission to make her will, which was a sensible precaution many women took while pregnant, given the manifold risks of childbirth. As a married woman, she needed her husband's permission to make a will. Edward's writ begins "Because we know well that nothing is as certain as death [pour ceo que nous savoms bien qe nule chose n'est si certeine come la mort], and nothing less certain than the hour when it may come, we give and grant permission for our very dear consort Isabella, queen of England, lady of Ireland and duchess of Aquitaine, that she may make and draw up her will..." 
Edward II left Windsor and travelled to Westminster for a few days in late October, returned to Windsor, and on 9 November left again and travelled to his palace of Sheen, twenty miles away. I wonder if this means that Edward III was a little premature, as it doesn't seem likely that Edward II would have left Windsor had his son's birth been believed to be imminent. Edward returned to Windsor on 12 November, maybe because he had been informed that the queen had gone into labour. In December 1312, Edward granted the enormous sum of eighty pounds annually for the rest of their lives to Isabella's steward John Launge and his wife Joan, Isabella's damsel - which gave them a higher income than many knights - "upon the said John bringing news of the birth of Edward the king's firstborn."  Whether this means that Launge rode from Windsor to Sheen to tell Edward that Isabella's labour had begun, or merely that he walked from one part of Windsor Castle to another to say to Edward 'wonderful news, my lord king, you have a healthy son', I don't know. (If the latter, that's got to be the easiest enormously high income anyone's ever earned.)
Off-topic here, but interesting: on 27 September 1315, Edward issued a "mandate for the arrest of Joan, wife of John Launge, going without the realm, and her detention until further order. The king is, without delay, to be certified of her arrest." She was, however, released from Rochester Castle and her goods and chattels restored to her on 17 October.  I have no idea what that was about.
The little heir to the throne was baptised three days after his birth in the chapel of St Edward the Confessor at Windsor Castle by Arnaud Nouvel, cardinal-bishop of St Prisca, a papal envoy then in England to negotiate between Edward II and the earls of Lancaster and Hereford and the other men who had taken part in Piers Gaveston's death. The boy had no fewer than seven godfathers: Arnaud d'Aux, bishop of Poitiers, chamberlain of Pope Clement V and another papal envoy trying to establish peace in England; John Droxford, bishop of Bath and Wells; Walter Reynolds, bishop of Worcester and soon to be archbishop of Canterbury; Louis, count of Evreux, the boy's great-uncle; John of Brittany, earl of Richmond, Edward II's first cousin; Aymer de Valence, earl of Pembroke, another close kinsman of the king; and Hugh Despenser the Elder, whom Edward of Windsor would see executed in his armour at Bristol a little less than fourteen years later. 
According to the St Albans chronicler, the French delegation wished the boy to be named Louis, but the English nobles forbade it, and he was named instead after his father, or perhaps his grandfather Edward I.  Both the Vita Edwardi Secundi and the St Albans chronicler say that little Edward's birth "much lessened the grief which had inflicted the king on Piers' death" and "tempered the sorrow he had felt since the death of Piers. On that day his love of the boy began and the memory of Piers began to vanish."  Of course this is an exaggeration, as Edward was still faithfully remembering Piers in numerous prayers at numerous religious houses many years later and clearly cherished his memory, but no doubt the chroniclers are correct in saying that Edward's joy at his son's birth did go some way to assuaging his terrible grief over Piers' death.
The Vita expressed a wish that Edward of Windsor would grow up to "follow the industry of King Henry II, the well-known valour of King Richard [Lionheart], may he reach the age of King Henry [III], revive the wisdom of King Edward [I], and remind us of the physical strength and comeliness of his father." Evidently, Edward II’s good looks and magnificent physique were the only positive attributes the author could think of to describe him. A few months later, the chronicler added "our King Edward has now reigned six full years and has till now achieved nothing praiseworthy or memorable, except that by a royal marriage he has raised up for himself a handsome son and heir to the throne." 
Isabella of France sent a letter (in French) to the city of London, announcing her son's birth: "Isabella, by the grace of God queen of England, lady of Ireland, and duchess of Aquitaine, to our well-beloved the mayor and aldermen and the commonalty of London, greeting. Forasmuch as we believe that you would willingly hear good tidings of us, we do make known to you that our Lord, of His grace, has delivered us of a son, on the 13th day of November, with safety to ourselves, and to the child. May our Lord preserve you."  The London annalist says that the city went wild with joy at the news, the inhabitants dancing in the streets and drinking huge amounts of free wine for a whole week.  Sounds like some party. Edward II granted his son the earldom of Chester when he was only a few days old, set up a household for him with dozens of servants, and granted him numerous lands, castles and manors. The king also granted Isabella lands in Kent, Oxfordshire, Derbyshire and Northamptonshire in 1313 and 1314, probably in gratitude that she had borne him a son.  Little Edward of Windsor grew up in the care of his nurse Margaret, wife of Stephen le Chaundeler, and his parents visited him occasionally. 
For all the contemporary criticism of Edward’s 'immoderate' and 'excessive' love for Piers Gaveston and all the opprobrium heaped on him nowadays for supposedly neglecting his poor tragic little wife (although the period from late June to early September 1312 was probably the longest time they'd ever spent apart since marrying in January 1308), by fathering a healthy, legitimate son Edward had done something only a handful of his earls had managed by November 1312. The obscure and insignificant earl of Oxford had a son, who was about the same age as Edward II, and the earl of Hereford had two, Edward’s nephews John and Humphrey de Bohun. According to one chronicle, Edward's nephew the earl of Gloucester had a son named John born in April 1312, but this is not confirmed by any other source, and if true, the boy must have died soon after, as Gloucester certainly died childless in June 1314. The earl of Arundel’s eldest son Richard was born in 1313 or the beginning of 1314 - he was said to be seven at the time of his wedding in February 1321 - and the earl of Warwick's in February 1314, even though Warwick was a dozen years older than Edward. The earls of Lancaster, Pembroke, Surrey and Richmond all died without legitimate children, and the earl of Lincoln, who died in early 1311, left only a daughter. (As did Piers Gaveston, earl of Cornwall.)
On 20 December 1312, Edward II paid the huge amount of 1249 pounds and 19 shillings for "cloth bought...for the liveries of the king, queen Isabel and Edward, the king's son, against the present Christmas." Edward, being perpetually skint thanks to the enormous debts left to him by his father and his own extravagance, had to borrow the money from his Italian bankers, the Bardi of Florence.  The king and queen of England, proud new parents, spent the festive season of 1312 at Windsor with the six-week-old baby who was already earl of Chester and one of the greatest and richest noblemen in the realm.
Further reading: Ian Mortimer, The Perfect King: The Life of Edward III, Father of the English Nation (2006)
1) Constance Bullock-Davies, A Register of Royal and Baronial Domestic Minstrels 1272-1327, p. 32.
2) Ibid., pp. 31-32.
3) Calendar of Patent Rolls 1307-1313, p. 508; Foedera 1307-1327, p. 184.
4) Cal Pat Rolls 1307-1313, pp. 516, 519; Calendar of Close Rolls 1313-1318, p. 54; Cal Pat Rolls 1321-1324, p. 128.
5) Cal Pat Rolls 1313-1317, p. 353; Cal Close Rolls 1313-1318, p. 253.
6) Cal Close Rolls 1307-1313, p. 558; Foedera, p. 187.
7) H. T. Riley, ed., Johannis de Trokelowe et Henrici de Blaneforde Chronica et Annales, p. 79.
8) N. Denholm-Young, ed., Vita Edwardi Secundi Monachi Cuiusdam Malmesberiensis, p. 36; Trokelowe, pp. 79-80.
9) Vita, pp. 36-37, 39-40.
10) Cited in Alison Weir, Isabella, She-Wolf of France, Queen of England, p. 71.
11) Annales Londonienses 1195-1330, in W. Stubbs, ed., Chronicles of the Reigns of Edward I and Edward II, vol. 1, pp. 220-221.
12) For example: Cal Pat Rolls 1313-1317, pp. 5, 38.
13) Calendar of Fine Rolls 1307-1319, p. 189.
14) Cal Fine Rolls 1307-1319, p. 158.