What is the importance of the House of Lords in the novel, That Self-Same Metal?

The House of Lords is where Joan confronts Auberon. Even though she defeats the Fae, Cecil tries to imprison her in his office and refuses to listen to her warnings about the gunpowder planted below. This leads to an explosion that kills Queen Anne, though Joan later learns that it was a ploy by Titanea to take the Queen’s place. However, most of the others in the House of Lords at the time survived, including Cecil and the rest of the King’s Men troupe.