Wyrd SistersBook - 1988
Witches are not by nature gregarious, and they certainly don't have leaders.
Granny Weatherwax was the most highly-regarded of the leaders they didn't have.
But even she found that meddling in royal politics was a lot more difficult than certain playwrights would have you believe...
WYRD SISTERS IS THE SIXTH NOVEL IN THE DISCWORLD SEQUENCE - THE FUNNIEST FANTASY SERIES EVER.