[mlangsdorf]

Originally Posted by Curmudgeon

1. Convince (or mind control) the king. Convincing the king implies that the PCs already have an advisory role to the king.

They're diplomatic envoys of a foreign power; they may be able to get an audience with the king and then cut a deal. It's probably not as good a deal as they could get from the heir-presumptive if the heir was king, but it's something they could do.

2. Appealing to parliament only works if a) there is a parliament and b) it is established as the supreme authority.

The English Parliament wasn't the supreme authority over James II, but when they invited William of Orange into the country and reinforced his army, James II abdicated.

3. The PCs need to be absolutely certain that the king’s assassination can’t be traced back to them.

There are downsides and risks to every approach the PCs can take.

4. Appealing to a foreign power or launching a rebellion are acts of treason. The PCs need to be successful.

Technically not treason, as the PCs aren't subjects of this kingdom, but losing wars is generally bad.

The PCs might consider proposing a regency by the heir presumptive for the king. The best argument would ostensibly be to provide the heir presumptive with actual experience ruling while the king is available to provide guidance.

Remember, the king in this instance is equivalent to Henry IV: a usurper who cut his nephew out of the line of succession and then convinced the aristocrats to support his rule. He wants to rule, and he's not going to turn over power to his nephew because he could have been the regent if he wanted, and he didn't want to do that.

One thing for the PCs to be wary of is getting the king to abdicate, if they are looking to put a friendly heir apparent on the throne. Abdication doesn’t just remove the king from the throne, it also removes his lineage from the throne.

So that's not necessarily true, and not a problem for the PCs anyway. The heir presumptive is the heir of the previous king, not the current king, and is a different lineage. In your example, he's Alex Windsor if Elizabeth had jumped line over Richard instead of inheriting in preference to Richard.

Kings are normally priests. (The taking of Holy Orders which makes one a priest is part of the Coronation ceremony.) Getting the king excommunicated might help.

There are reasons why this may not be easy, but it's something to think about it.

Other possibilities include arranging for a very public failure of the King’s Touch (healing) or a failure in the fertility of the land, either of which might indicate either a withdrawal, or the absence, of the Mandate of Heaven.

I think that's a variant of appeal to Parliament/the aristocracy: convince the peers of the realm that the current King isn't King, and it works out that the King is not longer King.