Guy Fawkes Day (or Guy Fawkes Night) commemorates the failure of the Gunpowder Plot of 1605, in which a group of provincial English Roman Catholics attempted to assassinate King James I by placing explosives beneath the House of Lords. A liturgy of Thanksgiving was introduced as part of the observances. The service was abolished in 1859 as being politically obsolete (and as an incitement of anti-Roman Catholic violence).
The following prayer is prescribed in the original 1662 Prayer Book for use at Holy Communion in place of the Collect for the Day.
Eternal God, and our most mightly protector, we thy unworthy servants do humbly present ourselves before thy Majesty, acknowledging thy power, wisdom, and goodness in preserving the King, and of the Three Estates of this Realm assembled in Parliament, from the destruction this day intended against them. Make us, we beseech thee, truly thankful for this thy great mercy towards us. Protect and defend our Sovereign Lord the King, and all the Royal Family from all treasons and conspiracies: Preserve them in thy faith, fear and love; prosper his Reign with long happiness here on earth; and crown him with everlasting glory hereafter in the kingdom of heaven; through Jesus Christ our only Saviour and Redeemer. Amen.