Catesby therefore planned a decapitation strike which he considered tyrannicide, aimed at the Government of England; by blowing up the King and the House of Lords with gunpowder during the State Opening of Parliament.

Concerns about possible collateral damage caused an anonymous letter of warning to be sent to William Parker, 4th Baron Monteagle, who alerted the authorities.

With a much-diminished group of followers, Catesby made a last stand at Holbeche House in Staffordshire (the modern-day Kingswinford suburb of Wall Heath), against a 200-strong Sheriff's posse led by Richard Walsh.

Catesby was mortally wounded by gunfire and later found dead inside Holbeche Hall, where he had died while contemplating a holy card of the Virgin Mary.

As a warning to other potential regicides, Catesby's body was exhumed, posthumously executed, and his severed head on a spike was displayed outside the Houses of Parliament.

[1] Those either studying at university or wishing to take public office could not do so without first swearing the Oath of Supremacy,[6] an act which would have compromised Catesby's Catholic faith.

[nb 1][11][better source needed] Katherine came from wealthy and respected Protestant dynasties and brought with her a dowry of £2,000, but also a religious association that offered Robert some respite from the recusancy laws then in effect.

[6] The rebellion was a failure, however, and the wounded Catesby was captured, imprisoned at the Wood Street Counter,[14] and fined 4,000 marks (approximately equivalent to £745,000 in 2023[nb 4][15]) by Elizabeth I.

Protestant rulers across Europe had, however, been the target of several assassination attempts during the late 16th century, and until the 1620s some English Catholics believed that regicide was justifiable to remove 'tyrants' from power.

[24] Shortly after he discovered that his wife Anne – who had been raised Lutheran and had abstained from the Anglican communion at her English coronation – had been sent a rosary from Pope Clement VIII, James exiled all Jesuits and other Catholic priests, and reimposed the collection of anti-Catholic fines.

[26] British author and historian Antonia Fraser describes Catesby's mentality as "that of the crusader who does not hesitate to employ the sword in the cause of values which he considers are spiritual".

[20] Writing after the events of 1604–1606, the Jesuit priest Father Tesimond's description of his friend was favourable: "his countenance was exceedingly noble and expressive ... his conversation and manners were peculiarly attractive and imposing, and that by the dignity of his character he exercised an irresistible influence over the minds of those who associated with him."

Following the Earl of Essex's failed rebellion, he had travelled to Spain to raise support for English Catholics, a mission which the authorities would later describe as comprising part of a 'Spanish Treason'.

Wintour, therefore, returned to the continent, where he tried unsuccessfully to persuade the affable Constable of Castile to press for good terms for English Catholics in forthcoming peace negotiations.

He then turned to Sir William Stanley, an English Catholic and veteran commander who had switched sides from England to Spain,[36] and the exiled Welsh spy Hugh Owen; both cast doubt on the plotters' chances of receiving Spanish support.

[47][48] Several months later, early in June 1605, Catesby met the principal Jesuit in England, Father Henry Garnet, on Thames Street in London.

[55] As their plans moved closer to fruition, during a secret meeting at Bath in August at which he, Percy and Thomas Wintour were present, the plotters decided that "the company being yet but few" he was to be allowed to "call in whom he thought best".

Catesby soon added Ambrose Rookwood, a staunch Catholic who was both young and wealthy, but who most importantly owned a stable of fine horses at Coldham.

[52] Although his account of the meeting is weighted with hindsight (when captured he sought to distance himself from the affair), he asked Catesby what support for the Catholics would be forthcoming once the king had been killed.

Catesby's answer, "The necessity of the Catholics [was such that] it must needs be done", in Fraser's opinion this demonstrates his unwavering view on the matter, held at least since his first meeting with Thomas Wintour early in 1604.

[56] The day after Tresham's recruitment, Catesby exchanged greetings in London with Fawkes's former employer, Lord Montagu, and asked him "The Parliament, I think, brings your lordship up now?"

[58] Several of the conspirators expressed worries about fellow Catholics who would be caught up in the planned explosion;[60] Percy was concerned for his patron, Northumberland, and when the young Earl of Arundel's name was mentioned Catesby suggested that a minor wound might keep him from the chamber on that day.

Together the two confronted the recently recruited conspirator, and threatened to "hang him", but Tresham managed to convince the pair that he had not written the letter, and the next day urged them to abandon the plot.

Although the nature of their discussion is unknown, Fraser theorises that some adjustment of their plan to abduct Princess Elizabeth may have occurred, as later accounts told how Percy had been seen at the Duke of York's lodgings, enquiring as to the movements of the king's daughter.

[66] Nicholls mentions that a week earlier—on the same day that Monteagle received his letter—Catesby was at White Webbs with Fawkes, to discuss kidnapping Prince Henry rather than Princess Elizabeth.

[68] On 6 November they raided Warwick Castle for supplies, taking cavalry horses from the stables to aid their escape,[69] before continuing to Norbrook to collect stored weapons.

Catesby gave Bates a letter to deliver to Father Garnet and the other priests at Coughton Court, informing them of what had transpired, and asking for their help in raising an army in Wales, where Catholic support was believed to be strong.

[70] Back in London, under pain of torture Fawkes had started to reveal what he knew, and on 7 November the government named Catesby as a wanted man.

Although gunpowder does not explode (unless physically contained), a spark from the fire landed on the powder and the resultant flames engulfed Catesby, Rookwood, Grant, and another man.

Robert Catesby's mother Anne was able to remain in Ashby St Legers due to her life interest, but after her death that property also passed to James I.