//// I thought defacing our banknotes was against the law (currency and banknotes act 1928) ////
Copied from the BBC website:
//// The Bank of England's website states that it is illegal to deface bank notes under the Currency & Banknotes Act 1928.
It says it is against the law to "deface our banknotes (by printing, writing or impressing upon them words, letters or figures, etc.), although the question of whether or not to prosecute in individual cases is up to the police and the courts".
In a statement, the gallery said it had contacted the Bank of England, which informed them that the notes were still legal tender.
It went on: "When it comes to the idea that this is currency defacement, it may well be in the eyes of the Bank of England, but to Graham and us at the gallery, we haven't done this maliciously, we've joined together for this event to bring goodwill to those lucky enough to find the notes."
They said their only motive was to spread "good faith and happiness" through the country. ////