Hints for Act III, Scene 3: Party Time:

Hint 1

Come to our party rooms! We serve fairy bread and pavlova and Victorian sponge and fixed terms...

Hint 2

These parties have been held at three houses — the House of Kirribilli, the House of Premier, and the House of Chequers.

Hint 3

The years correspond to elections and the colours correspond to political parties. Index the leaders to work out a phrase that clues for an “-ism”.