Thomas was an intelligent and educated man, fluent in several languages and trained as a lawyer, but chose instead to become a soldier, fighting for England in the Low Countries, France, and possibly in Central Europe.

Instead, in 1604 he decided to join with Catesby, who planned to restore England to Catholicism by killing the king and inciting a popular revolt in the Midlands, during which James's daughter, Princess Elizabeth, would be installed as titular queen.

The plot began to unravel following the delivery of an anonymous letter to William Parker, 4th Baron Monteagle, warning him to stay away from Parliament.

Catesby and most of the others spent two days travelling across the Midlands attempting to incite a rebellion, but with an ever-diminishing group of supporters they eventually settled at Holbeche House in Staffordshire, and waited for government forces to arrive.

[3] Their paternal grandparents were Robert Wintour of Cavewell in Gloucestershire, and his wife Catherine, daughter of Sir George Throckmorton of Coughton in Warwickshire.

[1] Their maternal uncle Francis Ingleby, a Catholic priest, was hanged, drawn and quartered at York in 1586, a fact which, in the opinion of historian and author Antonia Fraser, "could hardly have failed to leave a stark impression upon the Wintour family".

[12] I remained with my brother in the country for Allhollantide, in the year of our Lord 1603, the first of the King's reign, about which time, Mr. Catesby sent thither, entreating me to come to London, where he and other friends would be glad to see me.

At the second summons I presently came up and found him with Mr. John Wright at Lambeth, where he brake with me how necessary it was not to forsake my country (for he knew I had then a resolution to go over), but to deliver her from the servitude in which she remained, or at least to assist her with our uttermost endeavours.

Catesby sent a second letter that Thomas did respond to,[10] and when he arrived he found his cousin with John Wright, a devout Catholic and a renowned swordsman.

[15] He also offered a warning of the price of failure: "the scandal would be so great which the Catholic religion might hereby sustain, as not only our enemies, but our friends also would with good reason condemn us.

[16][17] In Flanders he met Juan Fernández de Velasco, 5th Duke of Frías and Constable of Castile, who was holding court there before his journey to England to conclude the Treaty of London.

Thomas again stressed the plight of English Catholics, hoping to influence the forthcoming treaty negotiations due to take place at Somerset House in London.

[19] Thomas also met the Welsh spy Hugh Owen, and Sir William Stanley, who were both disparaging of Catesby's hopes of Spanish assistance.

In late April therefore the two men returned together to Catesby's lodgings at Lambeth, and told him that despite positive noises from the Spanish, "the deeds would nott answere".

[nb 3][20][21][22] With the addition to the conspiracy of Thomas Percy (John Wright's brother-in-law), the five plotters met at the Duck and Drake inn, in the fashionable Strand district of London, on 20 May 1604.

[24][25] His confession has the plotters digging a tunnel toward their target during one of the several prorogations of Parliament,[nb 4] abandoned when the chamber directly beneath the House of Lords became available.

The latter's involvement in the plot has long been the subject of controversy, as on 26 October his brother-in-law William Parker, 4th Baron Monteagle, received an anonymous letter while at home, warning him to stay away from Parliament.

[31] His pleas were in vain; Catesby's position was echoed by Percy, who at a meeting of the three in London on Sunday 3 November, said that he was ready to "abide the uttermost trial".

[33] Monteagle had delivered the letter to the English Secretary of State, Robert Cecil, 1st Earl of Salisbury, and on Saturday 2 November (about a week later) the Privy Council decided to undertake a search of Parliament.

[34] The following Monday, during the first search, Thomas Howard, 1st Earl of Suffolk, noticed the huge pile of faggots in the corner of the cellar beneath the House of Lords.

In author Alan Haynes's opinion, this demonstrated an impressive degree of trust in Fawkes's ability to confound his interrogators,[36] but when Thomas heard for himself that the treason had been uncovered, he left for Huddington, stopping at his sister's house in Norbrook along the way.

[39] The next day the group raided Warwick Castle for supplies, something that Robert strongly objected to as it would create "a great uproar" in the country, and later arrived at Huddington Court, where they met Thomas.

While Littleton chose to leave, begging his companion to follow his example, Thomas continued on to Holbeche, where he found the remaining plotters alive, but injured.

[41][42] While several including Robert and his half-brother John chose to vanish into the night, Catesby, Percy, the Wright brothers, Grant, Rookwood and Thomas remained.

[47] Historically, much of what is written about the Gunpowder Plot is derived from Thomas's confession, signed on 23 November 1605; details of the so-called Spanish Treason were added three days later.

The signature, possibly forged by lieutenant of the Tower of London William Waad, was made only weeks after Thomas had been shot in the shoulder during the siege at Holbeche House.

Biographer Mark Nicholls views the difference in signatures as a significant and puzzling lapse, if a "master forger" is presumed to be responsible for the document.

He views the handwriting on the confession as "convincingly that of Winter [Wintour]", pointing out that it appears to be the work of an author, not an editor, and written as a draft for the King's Book.

[3] This is a view that generally, Alan Haynes agrees with: "no one has ever made a solid and sensible suggestion about why a government-employed forger (say Thomas Phelippes) would deliberately make such an error in a crucial state document".