Which palace did authorities search before arresting Guy Fawkes?

Authorities searched Westminster Palace—more commonly called the Palace of Westminster—before arresting Guy Fawkes.

The search took place in the early hours of 5 November 1605, after King James I was shown an anonymous warning letter received by Lord Monteagle. Sir Thomas Knyvet and his men inspected the undercroft beneath the parliamentary complex, where Fawkes was discovered guarding barrels of gunpowder.

The intended target was the House of Lords, then part of the Palace of Westminster. Fawkes was using the name John Johnson and carried a slow match and pocket watch. His arrest exposed the Gunpowder Plot, a conspiracy led by Robert Catesby and several English Catholics.

“Palace of Westminster” is the formal modern name; “Westminster Palace” is a common reversal and clearly identifies the same historic complex. The search was not at St James’s, Kensington or Hampton Court Palace.