The Gunpowder Plot was commemorated for years after the plot by special sermons and other public acts, such as the ringing of church bells. It added to an increasingly full calendar of Protestant celebrations which contributed to the national and religious life of seventeenth-century England. Through various permutations, this has evolved into the Bonfire Night of today.
Professor Ronald Hutton has considered the possible events which could have followed the successful implementation of the Gunpowder Plot, with the resultant destruction of Parliament and death of the king. He concluded that the violence of the act would have instead resulted in a more severe backlash against suspected Catholics. Without the involvement of some form of foreign aid, success would have been unlikely, as most Englishmen were loyal to the institution of the monarchy, despite differing religious convictions. England could very well have become a more "Puritan absolute monarchy", as "existed in Sweden, Denmark, Saxony, and Prussia in the seventeenth century", rather than follow the path of parliamentary and civil reform that it did.
When Parliament met in January 1606 for the first time after the plot they passed an Act of Parliament called the "Thanksgiving Act". This made services and sermons commemorating the Plot an annual feature on 5 November. The act remained in force until 1859. On 5 November 1605, it is said that the people of London celebrated the defeat of the plot with fires and street festivities. The tradition of marking the day with the ringing of church bells and bonfires started soon after the Plot and fireworks were also included in some of the earliest celebrations. In Britain the fifth of November is also called Bonfire Night, Fireworks Night or Guy Fawkes Night.
It remains the custom in Britain, on or around 5 November, to let off fireworks. Traditionally, in the weeks running up to the 5th, children made "guys"—effigies supposedly of Fawkes—usually made from old clothes stuffed with newspaper, and with a grotesque mask, to be burnt on 5 November bonfire. These effigies would be shown in the street, to collect money for fireworks, although this practice is becoming less common. The word "guy" came thus in the 19th century to mean an oddly dressed person, and in the 20th and 21st centuries to mean any male person.
Institutions and towns may hold firework displays and bonfire parties, and the same is done on a smaller scale in back gardens throughout the country. In some areas, particularly in Sussex, there are extensive processions, large bonfires and firework displays organised by local bonfire societies; the most extensive of which takes place in Lewes.
The Houses of Parliament are still searched by the Yeomen of the Guard before the State Opening of Parliament, however, this is done as a traditional custom rather than a serious anti-terrorist precaution.
A commemorative British two pound coin was issued in 2005 to celebrate the 400th anniversary of the plot.
The cellar in which Fawkes watched over his gunpowder was demolished in 1822. The area was further damaged in the 1834 fire and destroyed in the subsequent rebuilding of the Palace of Westminster. The lantern which Guy Fawkes carried in 1605 is in the Ashmolean Museum, Oxford. A key supposedly taken from him is in Speaker's House, Palace of Westminster. These two items were shown in a major exhibition held in Westminster Hall from July to November 2005.
According to Esther Forbes (a biographer), the Guy Fawkes Day celebration in the pre-revolutionary American Colonies was a very popular holiday. In Boston, the celebration took on anti-authoritarian overtones, and often became so dangerous that many would not venture out of their homes.
In November 1930, taking advantage of the bonfires used on the holiday, Alfred Arthur Rouse murdered an unknown man and planted his body as a substitute for Rouse's in his Morris Minor (1928) automobile (which was then set alight). The scheme did not work out, and Rouse was arrested, tried and executed for the crime.
Many at the time felt that Robert Cecil, 1st Earl of Salisbury had been involved in the plot to gain favour with the king and enact more stridently anti-Catholic legislation. Such theories alleged that Cecil had either actually invented the plot or allowed it to continue when his agents had already infiltrated it, for the purposes of propaganda. These rumours were the start of a long-lasting conspiracy theory about the plot. Yet while there was no "golden time" of "toleration" of Catholics which Father Garnet had hoped for at the start of James' reign, the legislative backlash had nothing to do with the plot: it had already happened by 1605, as recusancy fines were re-imposed and some priests expelled. There was no purge of Catholics from power and influence in the kingdom after the Gunpowder Plot, despite Puritan complaints. The reign of James I was, in fact, a time of relative leniency for Catholics, few being subject to prosecution.
This did not dissuade some from continuing to claim Cecil's involvement in the plot. In 1897 Father John Gerard of Stonyhurst College, namesake of a Jesuit priest who had performed Mass to some of the plotters, wrote an account called "What was the Gunpowder Plot?", alleging Cecil's culpability. This prompted a refutation later that year by Samuel Gardiner, who argued that Gerard had gone too far in trying to "wipe away the reproach" which the plot had exacted on generations of English Catholics. Gardiner portrayed Cecil as guilty of nothing more than opportunism. Subsequent attempts to prove Cecil's responsibility, such as Francis Edwards's 1969 work "Guy Fawkes: the real story of the gunpowder plot?", have similarly foundered on the lack of positive proof of any government involvement in setting up the plot. There has been little support by historians for the conspiracy theory since this time, other than to acknowledge that Cecil may have known about the plot some days before it was uncovered.
According to the historian Lady Antonia Fraser, the gunpowder was taken to the Tower of London magazine. It would have been reissued or sold for recycling if in good condition. Ordnance records for the Tower state that 18 hundredweight (equivalent to about 816 kg) of it was "decayed", which could imply that it was rendered harmless due to having separated into its component chemical parts, as happens with gunpowder when left to sit for too long—if Fawkes had ignited the gunpowder during the opening, it would only have resulted in a weak splutter. Alternatively, "decayed" may refer to the powder being damp and sticking together, making it unfit for use in firearms — in which case the explosive capabilities of the barrels would not have been significantly affected.
"", an ITV programme presented by Richard Hammond and broadcast on 1 November 2005, re-enacted the plot by blowing up an exact replica of the 17th-century House of Lords filled with test dummies, using the exact amount of gunpowder in the underground of the building. The dramatic experiment, conducted on the Advantica Spadeadam test site, proved unambiguously that the explosion would have killed all those attending the State Opening of Parliament in the Lords chamber.