Robert and Thomas Wintour the continent and again failed to elicit Spanish support, but instead met Guy Fawkes, with whom he returned to England. Robert, a devout Catholic who inherited Huddington Court near Worcester, joined the conspiracy the following year. 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. Thomas and Catesby confronted Monteagle's brother-in-law, the recently recruited Francis Tresham, threatening to kill him, but Tresham managed to convince them of his innocence. At that stage Thomas reportedly asked Catesby to abandon the scheme, to no avail. When
Robert and Thomas Wintour would nott answere". 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. From hereon Thomas Wintour remained at the heart of the conspiracy. The group leased properties in London, one in Lambeth for storing the gunpowder that was rowed across the Thames to its destination. His confession has the plotters digging a tunnel toward their target during one of the several prorogations of Parliament, abandoned when the chamber directly beneath the House of Lords became available.