Anarchy walks on 8 legs which are driven by a system of gears.

Each leg has 2 points of contact with the gears. The top of the leg is pinned to the gear to give you the up and down motion. The second is positioned about half way down the leg but the pin can slide freely up and down. It is the lower wheel that moves the leg back and forth creating the step.

You could do a walk on this system with just 4 legs but to smooth out the motion Anarchy has 8 with 4 legs on the ground at any one time so it doesn't rock about (to much...)

I hope that is vaguely helpful

EDIT: Lower down the page you can see a small image of Scuttles leg set up... it is the predecessor to Anarchy, only much much smaller. There was a Flash animation but its gone

http://www.bbc.co.uk/science/robots/tec ... case.shtml