On this day, January 18, in 1425, Edmund Mortimer, 5th Earl of March died at Trim Castle, on the south bank of the River Boyne in County Meath, Ireland. At the time of his death, Edmund was only a distant cousin of King Henry VI of England, with limited fortune and slim career prospects at court. However, he was a controversial figure in England and his death caused the royal family a certain amount of relief since some of his contemporaries maintained he, and not Henry VI, was the rightful king.

Henry VI’s grandfather, Henry IV, was the founder of the House of Lancaster after deposing the last Plantagenet king, Richard II, in 1399. Richard II’s claim to the throne was undeniable – he had been the only surviving son of the monarch’s eldest son (Edward, the Black Prince) – and he had smoothly inherited the throne from his grandfather, Edward III, in 1377 at 10 years old. It was less clear, however, who his own heir was since he, despite two marriages, was childless.

While today the laws of succession are clearly defined, it was bit murkier in the 14th century and Richard II’s own choice of his many uncles and cousins would have held significant sway, even if they were not next in birth order. The most powerful of Richard’s uncles – the sons of Edward III – was John of Gaunt, Duke of Lancaster. He was enormously wealthy, politically savvy and had decades of governing and military experience – he also had a capable heir, Henry of Bolingbroke, Duke of Hereford. However, Gaunt wasn’t popular with his nephew the King and there were many at court that mistrusted his ambition – afraid that he would end up with too much centralized power during Richard’s minority or, worse, would attempt to seize the throne for himself.

Despite this, and with huge significance, in an entail of the crown drafted in 1376/7 by Edward III before his death, he decreed that should his grandson die without any legitimate children, the throne should pass to Gaunt and his heirs. The problem with this is that, in addition to Richard II personally and professionally mistrusting his uncle of Gaunt, Edward III had effectively passed over the family of his second son, Lionel of Antwerp, Duke of Clarence, born in-between the Black Prince and Gaunt.

His reasons for doing so make sense, since at the time that Edward III wrote the entail, Lionel of Clarence had been dead for nearly a decade. He had been survived by a single legitimate child, a daughter named Philippa who would go on to marry a ward of Edward III’s, Edmund Mortimer, 3rd Earl of March. Since women were excluded from the succession of titles and there had never been a successful queen regnant of England, it makes a certain amount of sense that Edward III would skip over his granddaughter, despite the existence of her husband and sons.

However, the contents of the entail Edward III wrote were not widely-known. Members of the family likely knew what their patriarch’s wishes were, but they hadn’t been shared with the public. The hypothetical in which they dealt was also considered highly unlikely since it was assumed that Richard II, then a child, would go on to marry and successfully produce heirs.

Over 20 years later and Richard II had not only failed to produce heirs, but an entirely new generation had come of age. Philippa of Clarence’s eldest son was Roger Mortimer, 4th Earl of March and he went on to marry an heiress, Eleanor Holland. They had four surviving children – Edmund Mortimer, 5th Earl of March (and the subject of this post), his younger brother, Roger, and his two sisters, Anne and Eleanor Mortimer.

Thus, throughout the 1390s, many presumed that Roger Mortimer, 4th Earl of March was the heir of Richard II, while others thought it likely that the throne would pass to John of Gaunt, Duke of Lancaster. While Roger was descended from the “second son,” his claim was weakened by having been passed through a woman, while Gaunt was frequently out of royal favor and the “third son.”

In 1398 Roger Mortimer, 4th Earl of March died in Ireland and his title – and claim to the throne – passed to his son, Edmund, then only seven years old. The following year, Henry of Bolingbroke, Duke of Hereford – son and heir of Gaunt – found himself out of royal favor and was banished from England. While abroad, primarily in France, his father, Gaunt, died and Richard II barred him from inheriting the massive estate and fortunes that came with the duchy of Lancaster. Henry of Bolingbroke entered England illegally, on the pretense that he wanted only to take control of Lancaster, and ousted Richard II from the throne (we’re obviously simplifying this a bit for the purposes of focusing on March’s claim to the throne) and established the House of Lancaster and himself as Henry IV.

So, there are two ways of looking at the 1399 coup – a dynastic quick-fix that hurried up the line of succession already laid out by Edward III 20 years before OR a military coup that disregarded blood lines. Either way, it was a problem for Henry IV that not only was there a crowned king of England residing in his country, but there was a living male child that many believed to be Richard’s rightful heir.

Richard II was assassinated in February of 1400, which took care of that problem and Henry IV then turned his attention to Eleanor Holland, Countess of March and her four children. At the time, Eleanor’s two sons were taken into the King’s household and raised alongside his own children. Eleanor’s daughters, Anne and Eleanor, were left in her custody. Eleanor remarried, in 1399, to Edward, 5th Baron Cherleton and had two more daughters before dying in childbirth in 1405.

In 1402 Henry IV had a falling out with Edmund’s uncle, another Edmund Mortimer, younger brother of Roger Mortimer, 4th Earl of March. Angry with the king and married to the daughter of a Welsh rebel leader’s daughter (and therefore supplied with military support), Sir Edmund Mortimer declared his nephew the rightful heir to Richard II and therefore the true king of England. Edmund’s aunt, Eleanor Mortimer, was married to Henry Percy, son of the Earl of Northumberland, who supported a rebellion against Henry IV. This played out in 1403, reaching a crescendo at the Battle of Shrewsbury on July 21, during which the king successfully defeated the rebels.

The rebel alliance, however, survived. In 1405 Edmund and Roger were kidnapped from Henry IV’s custody at Windsor Castle, but quickly apprehended and returned. Edward, Duke of York, another grandson of Edward III, and his sister, Constance of York, were both held responsible and arrested. Because of this, and the death of their mother the same year, both boys were held under stricter custody for the remainder of Henry IV’s reign.

The fate of their sisters was less clear, who had been living with their mother until her death. Eleanor, the younger of the two, married Sir Edward de Courtenay before the end of 1409. The marriage ended childless in 1418 with Courtenay’s death. Anne, on the other hand, made a much more significant match: In May 1406, Anne married Richard of Conisburgh, the younger son of Edward of Langley, Duke of York and a great-grandson of Edward III through his fourth son, Edmund.

In March 1413, the Mortimers’ fortune changed again when Henry IV died at the Palace of Westminster and the throne was inherited by his eldest son, the new Henry V. One of the new king’s first acts was to release Edmund and his brother, Roger, on April 8, one day before his coronation. From this point forward there is no record of Roger and it’s believed that he died at some point in the year 1413. Edmund, on the other hand, was granted livery of his estates, swore an oath of loyalty to Henry V and was an active member of the royal court.

In January of 1415 Edmund received a papal dispensation to marry his second cousin, Anne Stafford. The marriage displeased Henry V, however, since Anne was also a descendant of Edward III, and therefore strengthened the claim to the throne of their hypothetical children. Though the couple was fined 10,000 marks for their marriage (effectively impoverishing them), they remained married.

In the spring of 1415 Parliament voted to go to war with France, allowing England to “re-conquer” French lands they believed rightfully theirs. By July, Henry V, leading nobles and the English army were in Southampton preparing to depart for France. It was there that, seemingly out of the blue, Edmund revealed to the king that there was a plot to depose him and put Edmund, himself, on the throne in his stead.

Behind this rebellion was Richard of Conisburgh, widower of Edmund’s sister, Anne. The year before, Richard had been named Earl of Cambridge – an honor, but one that carried with it significant expense to keep up. Since no lands or fortune accompanied the title, Richard, alongside several other nobles who chafed at the stinginess of the Lancastrian kings, had grown increasingly disillusioned with Henry V and, no doubt, ambitiously wanted his own family on and near the throne. Following his marriage to Anne Mortimer in 1406, the couple had two surviving children by 1415, Isabel (b. 1409), betrothed to the son of one of Richard’s co-conspirators, Sir Thomas Grey, and Richard (b. 1411). Following Richard’s birth, Anne had died, likely of childbed fever, and was buried at Kings Langley in Herfordshire.

At what point this plot took shape is unknown, as is what role various co-conspirators played. It appears that Richard of Conisburgh, Earl of Cambridge, didn’t share the plot with his elder brother, Edward, Duke of York, and it was largely shaped by him, Sir Thomas Grey and a third co-conspirator, Henry Scrope, Baron of Masham, who was a considered a close friend of Henry V. Nevertheless, on the evening of July 31, Edmund Mortimer shared the plot with the King, claiming to have just found out about it.

Cambridge, Scrope and Grey were arrested and a trial was immediately held in Southampton. Grey was executed on August 2, while Cambridge and Scrope, both peers, were beheaded on August 5. Edmund sat as a member of the jury that condemned his brother-in-law, before departing with Henry V and the army for France on August 11.

For the remainder of Edmund’s lifetime, that would be the end of it. The Southampton Plot, as it became known, proved his personal loyalty to the House of Lancaster and Henry V. He had no living brothers and he and his wife never had any surviving children. His closest male relative would be his orphaned nephew, Richard, thus diminishing the threat he posed to the crown.

In August 1422 Henry V died in France, having effectively conquered France. He had married Katherine of Valois, daughter of Charles VI, King of France, in June 1420 and their son was born in December 1421. Thus, at the time of his death, the throne passed to the nine-month-old, Henry VI.

A power struggle emerged at the royal court between the younger brothers of Henry V as Humphrey, Duke of Gloucester made a play for Lord Protector against John, Duke of Bedford. Edmund, refusing to support Gloucester, made a dangerous political enemy, though he was appointed to Henry VI’s Council of Regency in December 1422. The following May he was appointed Lieutenant of Ireland, however he didn’t leave England until the autumn of 1424 after arguing with Gloucester. He died shortly after his arrival on January 18, 1425 at Trim Castle.

Though the Mortimer family died with Edmund, his claim to the throne, of course, did not. Instead it passed on to his nephew, Richard, who was 14 at the time of his uncle’s death and the ward of Ralph Neville, Earl of Westmoreland. For two months after Henry V and the English army had departed for France in 1415 they had won of the Battle of Agincourt, during which Edward, Duke of York died, saving the life of his king. Childless, his only heir would have been his younger brother, recently executed at Southampton – thus, the duchy of York passed to Cambridge’s son, Richard. The son of a traitor, Richard could have been excluded from inheriting the title, but Henry V showed clemency given York’s heroism on the battlefield. Young Richard became the Duke of York at the age of four, inherited Edmund Mortimer’s claim to the throne at the age of 14 and married Westmoreland’s daughter, Cecily, at the age of 18, allying himself with a powerful, and large, northern family.

Richard, Duke of York, would, of course, become the patriarch of the House of York during the Wars of the Roses in their struggle against Henry VI and the House of Lancaster.

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