On 31 July 1415, the Southampton Plot had been revealed to King Henry V. Over the days that followed, the plot was investigated, trials were held and significant executions were ordered. The plot had been revealed to the king by Edmund Mortimer, 5th Earl of March, the main subject of the scheme, who also claimed he had no knowledge of it whatsoever.
The figure of Edmund Mortimer, dramatised in Shakespeare’s Henry V, has fascinated historians ever since. But who was he?
He was a significant claimant to the throne from a young age
Edmund’s story is fascinating, particularly with reference to the Princes in the Tower later in the century. In 1399, when Richard II was deposed by Henry IV, many would not have considered Henry to be the childless Richard’s heir. Henry was the son of Edward III’s third son, John of Gaunt. Edmund was a great-great-grandson of Edward III via that king’s second son, Lionel, Duke of Clarence.
In 1399, Edmund was seven years old, and had a younger brother named Roger. Their father had died the previous year, meaning that the issue of succession to Richard II in 1399 was less hotly contested than anticipated.
In 1399, Henry IV was faced with the question of what to do with two young boys who, in the minds of some, had a better claim to the throne than he did. Initially, they were kept in loose custody, then abducted in late 1405 or early 1406, but quickly recovered. The plan had been to get Edmund to Wales and declare him king in Henry’s place. After this, they were placed in stricter custody, eventually moving into the household of Henry’s heir, Prince Henry.
When the prince became King Henry V in 1413, he almost immediately freed the Mortimer brothers, allowing Edmund to take up his position as one of the wealthiest earls in England.
He reported a plot to make him king to Henry V
In 1415, Edmund exposed another plot to make him king to Henry V. He told the king that Edmund’s brother-in-law Richard of Conisburgh, Earl of Cambridge, along with Henry Scrope, 3rd Baron Scrope of Masham, and Sir Thomas Grey of Castle Heaton were behind the plan. The indictment against the three asserted that they planned to murder Henry V and his brothers in order to clear the path for Edmund to take the throne.
The news of the plot was brought to Henry V while he was in Southampton preparing to embark on an invasion of France, hence it being known as the Southampton Plot. It is said that the trial took place on the site of what is now the Red Lion Inn; however, there is little evidence to support this. On 2 August, Sir Thomas Grey was executed. Cambridge and Scrope were tried by their peers, as was their right as noblemen. There must have been little doubt of the outcome, and Cambridge pleaded guilty, appealing to the king for mercy.
Henry was not in a forgiving mood, and on 5 August 1415, Richard of Conisburgh and Lord Scrope were beheaded in front of Bargate in Southampton.
He remained loyal until his death
Henry then embarked on what would go down in history as the Agincourt campaign. If he had been assassinated, the course of the 15th century may well have been very different. The failure of the Southampton Plot had some far reaching consequences too. Edmund Mortimer lived until 1425, dying in Ireland while serving as Lord Lieutenant there. He had remained loyal to the Lancastrian regime despite his own claim to the throne.
The Mortimer claim continued to arouse suspicion
Richard of Conisburgh was not attainted, the process of conviction for treason by parliament that stripped a man and his descendants of lands and titles. Consiburgh’s only son was another Richard. Later in 1415, Conisburgh’s older brother Edward, Duke of York was killed at Agincourt, and his lands and titles passed to his nephew, who became Richard, 3rd Duke of York, a man who would become embroiled in the start of the Wars of the Roses until his death in 1460.
In 1425, York became even more significant with the death of his uncle Edmund, Earl of March. Edmund also had no children, so his lands and titles passed to his nephew Richard, Duke of York. With that immense wealth also came the Mortimer claim to the throne and all of the suspicion that engendered.
The fate of the Princes in the Tower was likely influenced by Mortimer’s claim
A large part of the reason York would fall into opposition to Henry VI’s government was that he was viewed with huge suspicion by a Lancastrian government that never shook off the fear of the Mortimer claim. Two of York’s sons would sit on the throne in Edward IV and Richard III. The fate of the Mortimer boys in 1399 and afterwards may have played into Richard III’s thinking about his young nephews, remembered as the Princes in the Tower. It was, after all, Richard’s own family history.
The part of Henry IV’s answer to the problem that hadn’t worked was keeping the boys in a well-known location and loosely guarded. It is perhaps therefore unsurprising that Richard kept the princes in the tower and their location entirely secret between 1483-5: he was determined to improve upon the mistakes of the past.