How a Syphon flush in a toilet works

We've been asked a few times to explain how a Syphon flush in a toilet works. In short a Syphon flush operates from the difference of pressure when the cistern handle is pumped, thus causing the water to 'Siphon' until it equalises in pressure or until the water has fully drained, see the hand picture attached. Did you know use of Siphons have existed since the 1500BC? It was even used in a Classical Era practical joke, the Pythagorean cup!