Richard II and Henry IV were first cousins, born in 1367 just three months apart. They were ten years old when Richard became king of England. They were 32 when, in 1399, Henry overthrew him to become ruler in his place.

It was a shocking and intensely dangerous moment. To understand why – what was at stake, and why the attempt to depose a king might threaten the security of the whole kingdom – we need to understand what the job of a medieval king was: where his authority came from, what he was required to do with it, and how his commands were enforced. In other words, we need to understand the late medieval constitution, meaning – in the words of a recent essay by Christine Carpenter and Andrew Spencer – ‘the set of political, governmental and legal structures and shared values within which the business of everyday politics and governance operate’.

I want to use the answers to those questions to tell the story of what went wrong with Richard II’s rule, and to explain why the attempt to set things right was itself both a terrifying process, and a damaging one. It’s a story about what happens when a ruler demands loyalty to himself as an individual, rather than duty to the established constitution; when he seeks to create his own reality rather than concede the force of verifiable truths; when he demands that his own will should trump the force of law; when he recognises no interests other than his own. It’s also a story about the unpredictability of unfolding political crises, and about the ways in which authority can be bent, shaped and broken. And its themes of power, legitimacy, and the limits of rule and resistance are as urgent now as they have ever been.

All those who claim sovereign power, whatever the time or place, seek legitimation from somewhere. In medieval England, the source of the crown’s authority was clear: the king was appointed by God to rule the kingdom and its people. His right to rule came with profound responsibilities, the most fundamental of which were shown on the most iconic image of power most of England’s people would ever have the chance to see: the king’s great seal, the physical manifestation of the crown’s authority by which royal commands were authenticated. On one side of the seal the king sat in state, orb and sceptre in his hands, to give law and justice to his subjects; on the other, he rode a warhorse, his sword unsheathed to defend his kingdom. As both judge and warrior, his task was to protect the realm from internal anarchy and from external attack.

But the king was only one man. However all-encompassing his authority might be in theory, how did he govern in practical fact? Fourteenth-century England was a remarkably centralised state with a complex bureaucracy, a sophisticated judicial system, and representative parliaments in which taxes were granted and statute law made – but it had no police force or standing army. For the enforcement of his rule, the king relied instead on the private power of the aristocracy, the great landowners whose estates gave them not only wealth, but control over the people who lived and worked on their land.

So why should the great landowners, with political and military muscle directly at their command, obey the king? They were rich and powerful men who wanted more wealth and power for themselves and their dynasties – but not, crucially, at the expense of the wealth and power they already had. They had everything to lose if the kingdom collapsed into anarchy or surrendered to foreign invasion, and everything to gain by upholding the hierarchy within which their own power was set, of which the crown was the keystone. This was pragmatism, but pragmatism that could not be separated from deeply held belief. If the authority of the king was instituted by God, then to depose him was to risk everything – worldly security and immortal soul – by challenging the order of God’s creation.

Such devastatingly radical action could never be justified unless kingship turned into tyranny: rule by arbitrary will rather than law, threatening the interests of kingdom and people instead of defending them. Even then, could anyone except God rightfully remove a sovereign He had anointed?

When Richard and Henry were born in 1367, that question had been answered in the affirmative only once in England in the three centuries since their ancestor William the Conqueror won his crown on the battlefield at Hastings. During the early decades of the 14th century, their great-grandfather, Edward II, had prioritised his favourites over the needs of his kingdom so consistently, to such appalling effect, that he undermined the rule of his own law. His wife led the resistance that, in 1327, put his teenage son on the throne in his place.

Since then, that new king had become one of the most extraordinary monarchs England had ever seen. Over the course of 40 years and counting, Richard and Henry’s grandfather, Edward III, had shown how powerful a king of England could be if he understood his responsibilities. His pursuit of war with France both reached for glory – in asserting his claim, inherited through his mother, to be king of France as well as England – and defended England’s shores by pushing the fight deep into French territory. And there was a great deal to show in return for the dreadful costs of war: victories in battle, and territorial and diplomatic gains, won by a king who offered decisive, responsive leadership at home as well as in the field. Certainly, his people believed that their fearsome and magnificent sovereign had ‘most tenderly at heart his land of England’, as his chancellor told a parliament held eight months before Richard’s birth.

Edward had shown just how powerful a king of England could be; but a structure of power which vested God-given authority in one man depended on that man to offer at least a bare minimum of leadership. By the 1370s that leadership was faltering. Edward was ageing and ailing. His eldest son, the Black Prince, was also seriously unwell. After the English triumphs of the 1340s and 1350s, and an ill-starred attempt at peace in the 1360s, the new phase of the war was going badly, and the king’s next oldest son, John of Gaunt, Duke of Lancaster – trying desperately to hold the regime together in the name of his father and brother – became a lightning rod for political blame.

In 1376 the Black Prince died, followed a year later by his father, and England had to face a stark new reality. Edward III had ruled for half a century; almost no one could remember a time when the crown had been worn by anyone else. But now it would come to rest on the head of a ten-year-old boy: the Black Prince’s only legitimate child, Richard. In one sense, the hereditary principle had done its work. There was no argument over the succession: the people of England transferred their loyalty without question to the new King Richard II as ‘the true heir apparent of the realm’. But the ‘true heir’ was ten. A way would have to be found to keep government going without him until he was old enough to take charge.

In theory, the obvious answer was that John of Gaunt should serve as regent, as the king’s oldest surviving uncle and the kingdom’s most powerful magnate. But in practice Gaunt was too unpopular: not only blamed for military failure and high taxation, but unfairly suspected of wanting to make himself king in his nephew’s place. At the same time, he was too powerful for anyone else to be installed as regent over his head. The only workable solution was to fudge the issue. Officially, there would be no minority; the ten-year-old king would rule. Unofficially, decisions taken in the king’s name would be made by his nobles.

A young man growing to adulthood who understood the responsibilities as well as the rights of his crown might have come to understand why misrepresenting political reality in that way was necessary, and what he had to do to take command when the time came. Richard was not that man. For as long as he could remember, Richard had known that he was special. As the one ‘true heir’ of his father and grandfather, he was unique and irreplaceable. But he had never seen kingship in action because, for as long as he could remember, his father and grandfather had been too ill to lead England’s government. In their attempt to unite the country, Gaunt and the other lords trying to keep the war effort going had presented Richard to Parliament in January 1377 as a boy sent by his grandfather ‘in the same manner as the scripture says, “Here is my beloved Son, here is He who is wished for by all men”’. Seasoned politicians might recognise overblown rhetoric, but Richard heard the message that he was England’s messiah.

When Edward III died that summer, the new little king was anointed and crowned in Westminster Abbey, an intoxicating ceremony that reinforced his growing sense of his own majesty. Four years after that, during the chaos and violence of the Peasants’ Revolt, Richard found that Wat Tyler’s rebels were looking to him for leadership. They stood, they said, ‘with King Richard and the true commons’ against what they saw as a corrupt and failing government.

Richard agreed. The government carried out in his name, he believed, was corrupt and failing, but his conclusion was not that he must learn to rule his people well. As he grew older, his obsession with the rights of his crown was not matched by any understanding of its duties. He had no interest in the challenging substance of government: in fighting to defend his kingdom, in the hard work of negotiating peace, or in the importance of law and justice. Instead, what had gone wrong in England, he thought, was that his nobles had usurped his own God-given authority.

The decades-long conflict with France was now going so badly that the treasury was empty, English territories on the continent were falling to the French, and the south coast was repeatedly damaged by French raids. The war was no longer happening ‘over there’: it had come home to roost. But, to Richard, it was a tedious irrelevance.

Instead, in 1384 and 1385, while Gaunt tried to defend the north against the Scots and find terms for peace with the French, Richard and his favourites within the royal household were plotting – unsuccessfully – to murder him. In 1386, with Gaunt by now fighting abroad, a parliament led by Richard’s youngest uncle, Thomas of Woodstock, tried to force the 19-year-old king to focus on the imminent threat of invasion by a French armada. Richard’s furious response was that he would ask for help against Parliament’s insolence from his ‘cousin’ the French king, ‘and rather submit ourselves to him than succumb to our own subjects’.

It was a shocking demonstration that Richard had grown into a thin-skinned narcissist, whose understanding of power was focused entirely on his own will rather than the needs of his people. Not only was the king failing to defend his kingdom from the coming attack, but – at this of all possible moments – he was choosing to suggest that his subjects were his enemy, and England’s enemy his friend.

Thomas of Woodstock’s response was terse. If the king would not accept good advice, then good advice must be imposed on him, in the form of a council appointed by Parliament for a year to oversee every aspect of the royal administration. It was not simple to impose restrictions on the king, but needs must – and, given the extremity of Richard’s response to those who had tried to make him recognise reality, the council’s work continued even when the French armada was thwarted by the weather. It had to be hoped that the young king might learn his lesson by the time the council’s year in office was done.

Instead, Richard upped the ante. He refused to cooperate with the council, removing himself from Westminster and declaring that all those who had supported the council’s appointment should be punished as traitors. Treason was the worst of all crimes, carrying the worst of all punishments: a hideous death for the traitor himself, and the destruction of his line through the permanent forfeiture of his estates. For that reason, it had been closely defined by Edward III in a statute of 1352, but Richard was now taking the definition of treason entirely into his own hands. Anyone who forced or incited the king to do something against his will, he said, should be punished as a traitor. And who could determine if the king had done something against his will apart from the monarch himself?

When Richard returned to London in November 1387, his lords had a frightening choice: submit, in the fragile hope that the king could be persuaded into greater wisdom; or arm themselves against him in the attempt to force him back into line. Most kept their heads down, but three noblemen – the king’s uncle Thomas of Woodstock and the earls of Arundel and Warwick – chose resistance. They were trying, they said, to remove the favourites around the king who were the real traitors to the realm. This deflection of blame from Richard himself was a desperate attempt to protect themselves from charges of treason. It also reflected the fact that Richard had no son or brother, no unquestioned heir – and it was impossible, therefore, to agree whether or how any of his uncles or cousins might replace him.

But no deflection could avert the confrontation that was coming – and when it became clear that negotiations could not work because Richard’s word could not be trusted, two younger lords joined Woodstock, Arundel and Warwick in rebellion: Thomas Mowbray, Earl of Nottingham, and Richard’s cousin, Gaunt’s son, Henry of Bolingbroke. Henry led the forces that defeated Richard’s favourite Robert de Vere at the battle of Radcot Bridge and drove de Vere into exile. In 1388, at what became known as the ‘Merciless Parliament’, Henry and his allies charged Richard’s closest advisers with treason and presided over a spate of executions.

They were playing a profoundly dangerous game. Richard had sought to rewrite the law of treason, and with it the entire basis of the relationship between his crown, his subjects and the law. But it was the rebel lords, in trying to stop him, who had first put an army into the field, and held show trials leading to the gallows and the block. For now, Richard had no choice but to comply, but if a lasting peace were to be restored, some way would have to be found to draw a line under the conflict.

In 1389, Richard made his move, reclaiming his place at the head of ‘normal’ royal government with the help of the newly returned and always dutiful Gaunt. While he slowly rebuilt his regime, his cousin Henry took the chance to seek adventure – and put some distance between himself and the king – by fighting in Lithuania with the crusading order of Teutonic Knights, then travelling as a glamorous pilgrim through the courts of Europe to Jerusalem.

Richard, meanwhile, was seeking to free himself from the financial and political constraints that had forced him to submit to his subjects’ control. A permanent peace with France could not be found, but a 28-year truce – sealed in 1396 by Richard’s glittering wedding to Isabella, the six-year-old daughter of the French king – called a halt to the war, and filled Richard’s treasury with gold from the little girl’s dowry. He adopted a new badge, the white hart, which he plastered across the palaces and churches of his kingdom. It was a badge that would also be worn by people: a new retinue of knights and archers who answered only to his personal authority. In theory, a king could call on the service of all his people; the unnerving question raised by this private army, therefore, was why Richard thought he needed it, and what he intended to use it for.

The lesson he had learned, it turned out, was not the one his subjects had hoped. In 1397 he launched a terrifying coup within his own kingdom. Woodstock, Arundel and Warwick were arrested and charged with treason for their actions ten years earlier, actions for which the pardons they had received were not, in Richard’s brave new world, worth the parchment on which they were written. Warwick was sentenced to life imprisonment. Arundel was beheaded on Tower Hill. And Woodstock – son of Edward III, uncle of the king himself – was murdered behind the walls of his Calais prison.

Their junior partners of ten years before, Henry and Thomas Mowbray, were untouched so far, but found themselves in an appallingly compromised position. In the attempt to save themselves, they had been complicit in the destruction of Woodstock, Arundel and Warwick; but Richard had already gone back on his word so many times that they were terrified of what might follow. While Richard tightened his grip on England through military force and judicial insecurity, fear drove Henry and Mowbray to accuse one another of treachery. Richard decreed that the truth should be tried by combat – but when the two men came face to face in the lists at Coventry in 1398, the king stopped the duel and banished them both from England.

England was through the looking-glass. Three of the kingdom’s greatest nobles had already been destroyed. Now two more were banished without being tried or convicted of any offence. No royal judgement, no royal promise, it seemed, could ever be trusted. Richard declared that Henry and Mowbray in exile would be allowed to take possession of any lands they might inherit back in England – but once again Richard lied. When Gaunt died in February 1399, the king took the vast estates of Henry’s Duchy of Lancaster into his own possession. Then, believing he had destroyed the power of the cousin he hated, Richard sailed with his army for Ireland, where he had already enjoyed watching the Irish chiefs kneel in homage before him a few years earlier.

Richard did not realise that, in disinheriting Henry, what he had destroyed was the foundation of his own rule. If the greatest nobleman in England could not rely on the protection of the law against the king’s arbitrary will, then no one could. Richard had demonstrated in the clearest possible terms that there could be no security for any of his subjects while he still wore the crown. And if the king no longer offered his subjects security – if, in fact, he actively threatened it – then the constitution, the structures and shared values that allowed government to function, was broken.

England’s people looked for rescue to Henry, the ‘eagle duke’ (as one poet called him, after a badge his father and grandfather had used): the one man, after all the deaths of the previous two years, who could offer leadership in resistance to the king’s new world order. When Henry returned from exile with a small band of loyal followers – to claim his inheritance, he said – England rallied to his banner. By the time Richard managed to return from Ireland, his kingdom was already lost.

It was a matter of practical necessity that Richard must be removed from the throne. It was a matter of practical fact that Henry was the only possible candidate to rule in his place. Still, removing the crown from an anointed king and putting it on another head was no simple task. If the keystone fell, would the hierarchy of the state collapse with it?

Thirty-three articles of accusation against Richard were drafted to justify his deposition; they returned again and again to his perjury in breaking the oath he had sworn at his coronation to uphold the law and do justice within his realm. Instead, he had declared, they said, ‘that his laws were in his own mouth’, and that the lives and property of his people ‘were his, and subject to his will’.

Even so, if a king was made by God, by what earthly authority could he be unmade? Richard, it was decided, must abdicate, as well as being deposed. He tried to resist, but the outcome was brutally clear: he had no alternative. On 29 September 1399 Richard resigned the throne. On 13 October, Henry was crowned Henry IV in Westminster Abbey.

The one attribute of sovereignty Henry lacked was the one Richard still had: the legitimacy of birthright. A king who had become a tyrant was replaced by a king who was a usurper – and that meant Henry’s throne would always be vulnerable. Just how vulnerable became obvious less than three months later when the handful of nobles who had been closest to Richard rose in revolt. The rebellion was put down, but the danger of a living ex-king was clear. Within weeks it was announced that Richard had died in his prison – starved to death, rumour said. In order to save England from Richard’s tyranny, Henry had not only done what his cousin had always feared – usurped his power – but committed the sin of regicide.

A man who believed in justice, and in the sacred authority of kingship, had been forced to violate both in his attempt to preserve the kingdom. Henry would spend his reign trying to escape Richard’s shadow, in the hope that his own good government might one day demonstrate God’s blessing and justify his claim to England’s throne.

He never quite succeeded. His usurpation made him vulnerable: anyone who felt dissatisfied with his rule could, and did, use the questionable legitimacy of his crown as justification for rebellion. It was not until 1408 – after years of firefighting against internal revolt and external attacks by the Scots and the French – that England finally found an unsteady peace. By then, Henry’s health had collapsed. His enemies were quick to see his suffering as evidence of God’s judgement. And when he died at the age of just 45, his son – one of the most able men ever to wear the crown, who sought to present himself as the rightful heir of both Henry and Richard – had to face one more conspiracy before the last embers of the conflagration of 1399 were finally extinguished.

From a distance of 600 years, we can see what happened in 1399. Richard’s attempt to reject the crown’s duties to its subjects – or, in his view, to seize the power he believed was rightfully his – ultimately failed. His fall served to strengthen precedents that bound the king to uphold the law and defend the interests of his people, and in turn became a powerful precedent itself: the events of Richard’s reign were repeatedly cited by opponents of Charles I in the 1640s.

But being able to see, with hindsight, what happened doesn’t mean that it was inevitable; nor does it mean that it came without profound costs. Thanks to the 16th-century world-view that we’ve inherited most powerfully through Shakespeare, Richard’s deposition and Henry’s usurpation are often framed as the root of civil war, the bloody conflict of the Wars of the Roses that ended only with the coming of the Tudors. But there is another framing, another question to be asked: what would have happened to England if Richard had not been removed?

Like all of the past, the story of Richard II and Henry IV gives us not answers, but warnings. It warns us not to assume that political structures or norms are immutable or eternal, especially if those in power set out to break them – and that the attempt to save them might mean breaking more, with consequences that aren’t easy to foresee. And it tells us that whenever truth, material reality and history itself become politically contested terms, we should pay very close attention indeed.

The Lancaster History Lecture 2025 was given by Helen Castor in the Faraday Lecture Theatre at Lancaster University on 12 March. The lecture, a collaboration between Lancaster University and Litfest (Lancaster Literature Festival) can be viewed via www.litfest.org. Helen Castor’s book, The Eagle and the Hart: The Tragedy of Richard II and Henry IV, is published by Penguin and can be ordered online.