THE setting was Southampton. The nation was preparing for war with France. But unbeknown to the King some of his most trusted supporters were plotting nothing less than his overthrow and murder.

But it was the plotters who were to meet a gruesome fate: beheaded in public in the city some 600 years ago.

Had events unfolded differently in Southampton that autumn in 1415 there might never have been a victory at Agincourt.

Henry V is remembered by history as England’s Warrior King. His defeat of the French army at Agincourt on October 25, 1415 has been immortalised by Shakespeare and is taught to every English school pupil.

Trapped by a much larger force of 30,000 French knights and men at arms, Henry and his small army of less than 10,000 men, including several hundred Welsh bowmen, made their stand near the village of Agincourt.

The result was a rout of the French army as wave upon wave of longbow arrows toppled charging knights from their steeds as they attempted to cross the boggy land towards where Henry and his men stood behind lines of sharpened wooden stakes. The attack turned into a massacre as more French men at arms followed on foot, each wave falling over the bodies of those who had already been brought down.

By the end of the battle an estimated 11,000 French soldiers had died, including some of the greatest princes of the land. Although estimates for the English and Welsh dead were played down, and even taking the figure recorded at the time of a mere 40 men killed with a pinch of salt, Henry would have lost no more than 100 or so.

But the battle may not even have happened had it not been for an extraordinary last-minute confession on the eve of the invasion fleet leaving Southampton Water by one of Henry’s closest rivals to the throne.

Henry had come to the throne on the death of his father Henry IV, bringing to an end decades of civil war between the most powerful noble houses in the land. The successful transfer of the crown from father to son seemed to stabilise the country.

Feeling safe at home, Henry decided to pursue his claim to the French throne.

Despite attempts by the French to dissuade him from invasion by treaty, Henry gathered his army at Southampton and prepared to sail.

Southampton was, at the time, England’s foremost fortified port. It had been strengthened following French raids in the previous century and Henry had also ordered to building of the God’s House Tower – still standing – to house his armoury.

The city would have been a bustling, noisy, smelly place as thousands of soldiers and their hangers-on arrived in Hampshire. To feed the army Henry had ordered great herds of cattle to be brought to the area, and the army would have been supported by all manner of tradesmen.

The friction between townsfolk and the King’s great gathering must have been immense.

But Henry’s presence alone would have been enough to keep order. Not the most handsome of men, his face bore the deep, ugly scar of an arrow that had been removed after he was shot in the head.

Splitting his time between castles at Winchester – where he had met French envoys for the last time – Portchester and Southampton, Henry began his final arrangements to sail for the French coast.

However, as summer turned to autumn he was shaken by a visit on the very day before his army was to embark by the young Earl of March, Edmund Mortimer, 23.

He informed a shocked King that not only was there a plot afoot to remove him from the throne, but that Mortimer himself was to be crowned in his place. Throwing himself on the King’s mercy he revealed the names of those plotting to put him on the throne.

The King was stunned. The names included some of the most prominent men in the land, including Richard Earl of Cambridge the younger brother of the Duke of York, Sir Thomas Grey, and one of Henry’s closest advisors Henry, Lord Scrope. The plan, an amazed Henry was informed, included raising a rebellion in Wales, bribing the Scots to invade the north of England, and the return of several renegade lords who would raise an English army to topple Henry.

It all made sense. With an army gathered at Southampton ready to invade France the plotters could strike quickly.

Henry, not surprisingly, struck first. The King arrested the named conspirators and ordered their immediate trial at Southampton. They were imprisoned in the new God’s House Tower.

Henry had the men charged with high treason and they were accused specifically of plotting to assassinate the king.

Sir Thomas Grey pleaded guilty and was immediately beheaded. Cambridge and Scrope, as nobility, demanded to be tried by their peers and a hearing was organised in the city. It was arranged quickly as most of the nobility were present with the army.

A jury of 20 peers, including the King’s brothers – the dukes of Clarence and Gloucester took part. Cambridge’s brother, the Duke of York, was permitted to be absent for obvious reasons.

Scrope argued that he had not acted treasonably and his only crime was to not report the plan to the King. Cambridge admitted his part fully.

Both men were condemned to death to be drawn, hanged and beheaded where the accused would be dragged through the streets by a horse, hung until almost dead and their head then removed. (This differed to being hung, drawn and quartered where the entrails were removed while the accused was still alive, before being hung and then chopped into quarters.) In his mercy the King reduced Cambridge’s sentence to a simple beheading. Cambridge wrote a grovelling letter to Henry – ‘Mine most dreadful and sovereign liege Lord’ – asking to be spared. The King was having none of it and his head was taken off.

For Scrope there was to be even less mercy. The King was annoyed his most trusted advisor had betrayed him. There was also a suspicion that French gold was behind the plot and as Scrope had carried out the negotiations for Henry in France he would have been in the best position to instigate the whole affair. Scrope was dragged from the God’s House Tower, hung in public and then beheaded.

Two days later Edward Mortimer received a royal pardon, the King believing he was an innocent in the affair that might have put him on the throne.

Having dealt with the plot the King left Southampton with his fleet and his army for glory at Agincourt.

As a final ironic twist, one the few English nobles to die at Agincourt was Cambridge’s own brother the Duke of York.

Had he not plotted against Henry then Cambridge would have inherited his brother’s title and lands and all the wealth and prestige he hoped to gain from rebellion.