soup wrote:

Mary Pegg popped their head over the parapet saw what was going on and
said
Mary Pegg wrote:

[fx: thinks] So the water is meant to travel around the rim and
*then* enter the bowl? So the problem lies at the front?

Golly! A Flash animation that's actually useful! See he
http://home.howstuffworks.com/toilet1.htm

I have never dealt with a cistern like that (leftpondian ?)
there appears to be no siphon merely some sort of flap
valve controlling the flush.

Very much like the Fluidmaster valve, but the links lower down to Faucet
this and that do suggest usanian origins.