Mark - you've excelled yourself with this one!
I could only get a short way into the start before I needed your help with that very devious first section. Thanks for showing me the way.
After that there were quite a few mishaps before I worked out the right way to do it, only to find I was stranded at the very end
Back to the drawing board, I finally made it.
Wonderful and very clever.
Thanks for giving us yet another tour de force!
