On 26 October an anonymous letter warned Lord Monteagle to avoid the opening of Parliament. This letter was possibly sent by Monteagle's brother-in-law, Francis Tresham. In any event it caused enough suspicion that on the night of 4 November the undercroft beneath the House of Lords was searched by guards, where Guy Fawkes was found in possession of matches and gunpowder was found hidden under coal. After intense torture in the Tower of London Fawkes gave his true name and those of his fellow conspirators. All but one of the plotters pleaded not guilty but nevertheless the seven were found guilty of high treason and each were executed on 30 and 31 January.