1 Merlin: So, what I don't understand is you sat in the Siege Perilous, yet you still live.
1 Prof. Jones: What's the problem?
2 Merlin: I enchanted it myself! It slays all except the one destined to find the Holy Grail!
3 Prof. Jones: Oh, is that all? I found that years ago.
4 Merlin: Oh? Phew, I thought maybe my spell was a botch job.

It would be a rather awkward piece of furniture to keep around the house. Or castle, as the case may be.

I mean, how many times do you have a chair that you really really don't want anyone to sit on, yet someone goes and sits on it anyway?

I can see an awful lot of hands up out there.

King Arthur must have been sweeping dead people out of the castle at a rate of a couple every month, at least.