Library curators have found a box with gunpowder samples as they worked their way through a collection of 17th century documents which the British Library acquired a couple of years ago.
One of the samples has a note saying "Guy Fawke's gunpowder" attached to it. The note was written about 100 years ago, and might point at gunpowder which a Catholic group around Guy Fawkes wanted to use to blow up King James I and Parliament.