Edmund de Mortimer, 5th Earl of March and 7th Earl of Ulster, was born on 6 November 1391, at New Forest, Westmeath, in Ireland, the eldest son of Roger Mortimer, 4th Earl of March, and Eleanor Holland.

The newborn baby Edmund was third in line to the throne while King Richard II lived. His father, the heir presumptive, was the grandson of Philippa of Clarence, was the only child of King Edward III’s second surviving son, Lionel of Antwerp, 1st Duke of Clarence. Little Edmund’s mother was also carried royal blood, since she was was the granddaughter of Joan of Kent, and who was in turn a granddaughter of King Edward I.

Then when Edmund was only 8 years old, his cousin Henry of Bolingbroke usurped King Richard II’s throne and became King Henry IV. This put Edmund and a very dangerous position, because since his father’s death the year before he had become the most legitimate claimant to the crown. He had much more right to it than the monarch currently wearing it.

Seeing Edmund and his little brother Roger as the threats that they were, King Henry IV put the little boys into the custody of Sir Hugh Waterton. It would have been very easy for them to ‘disappear’ as later heirs would, but happily “they were treated honourably, and for part of the time brought up with the King Henry IV’s own children, John and Philippa.”

Sadly for everyone, Henry IV was a crappy king. Not only was he a usurper, he was more bombastic than fantastic at ruling. This meant that there was a lot of instability as everyone saw their chance to make a grab for the crown. If Henry of Bolingbroke could do it, why not someone else?

Henry knew his seat on the throne was precarious, and he desperately wanted to get rid of those who might threaten his reign, but he went about it in a manner guaranteed to lose his allies. For example, when Sir Edmund Mortimer, son of the 3rd Earl and uncle of Edmund the 5th Earl, was captured by Welsh resistance fighter Owain Glyndŵr on 22 June 1402, King Henry refused to ransom him. Perhaps he was hoping Owain Glyndŵr would kill Sir Edmund, and eliminate the threat he posed? Then, to add insult to injury Henry tried to escape critique for abandoning a loyal fighter by claiming Sir Edmund hadn’t been captured, but had instead defected to Owain Glyndŵr’s team. This also gave Henry the false justification to confiscate Sir Edmund’s land.

Rather than solving a problem for King Henry, this nearly cost the foolish king his crown. Sir Edmund had been loyal up to then, and showed no signs of making a play for the throne, but now he was vexed beyond the telling. Sir Edmund promptly became an ally with Wales in truth, sealed their pact by marring Glyndŵr’s daughter, and “on 13 December 1402 proclaimed in writing that his nephew Edmund was the rightful heir to King Richard II.” Moreover, Sir Edmund arranged for his sister to wed Henry ‘Hotspur’ Percy, son of the Earl of Northumberland, and get the powerful Percy family to join the rebellion against Henry IV. Glyndŵr, Sir Edmund, and Hotspur all agreed to split the kingdom up when Henry IV was deposed, with the North going to the Percys, the South going to the new king, Edmund the 5th Earl of March, and Wales staying with Glyndŵr.

Henry’s ploy to kill Sir Edmund had precipitated a civil war.

Luck, however, was on the king’s side. Hotspur was defeated and slain at Shrewsbury, and although the future Henry V was badly wounded, the heir to Henry’s crown survived. Nevertheless, Hotspur’s death didn’t stop the war.

After the Battle of Shrewsbury, Glyndŵr, Sir Edmund, and the Percys decided that they need to rescue Edmund and his brother Roger from King Henry and bring them into Wales. That way the children would be safe from any retaliation by King Henry, and young Edmund could act as a figurehead and alternate King of England. The conspirators managed to free the boys on 13 February 1405, but again all the luck was on King Henry’s side, since his allies quickly recaptured Edmund and Roger near Cheltenham.

Constance of York was held responsible and arrested. She implicated her brother, the Duke of York, who was imprisoned at Pevensey Castle for seventeen weeks. As a result of the failed abduction, on 1 February 1406 Edmund and Roger were put under stricter supervision at Pevensey Castle under Sir John Pelham, where they remained until … 1 February 1409 [when they] were given in charge to the King’s son, the Prince of Wales, who was only five years older than Edmund. They remained in custody for the remainder of Henry IV’s reign.

If the boys had been smuggled safely into Wales, if there had been a clear alternative king to put on the throne, would the rebellions against Henry IV have been successful? It is bizarre to think of how close British history came to an independent Wales and a divided England ruled by King Edmund I.

Henry V was a much better king than his father. In fact, the only reason Henry IV was able to keep his throne was because Henry V had preemptively taken power after 1410 while still the Prince of Wales. As king, Henry V wisely bound the Mortimer’s to him by kindness and respect. One of his first acts as king was to free Edmund and Roger de Mortimer and make them Knights of the Bath. Although Edmund would marry to closely to the throne for Henry’s liking, and was the unknowing would-be beneficiary of the Southampton Plot, Mortimer was always loyal to his king. “He never made any claim to the throne, despite being senior in descent” and he became “one of Henry’s most trusted counsellors.” Mortimer even served on the Council of Regency for King Henry VI, yet never tried to usurp the infant’s throne.

Edmund de Mortimer died in January 1425 of the plague while at Trim Castle serving as the Lord Lieutenant of Ireland. Since Edmund was childless, his estates and titles were passed to his sister Anne’s son, Richard Plantagenet, 3rd Duke of York. This same Duke of York was now the only male who could claim decent from Lionel of Antwerp. York’s eldest son would eventually become King Edward IV after overthrowing Henry IV’s grandson and killing his great-grandson, Edward of Westminster.

Henry IV had been right to fear the Mortimer line. Of course, if Henry hadn’t stolen the throne from his cousin Richard II in the first place, then his descendants wouldn’t have died vying for a crown that should have never been theirs.