ok guys i use the london position quite alot and its a staple of my guard game.
First of all forgive my criticisms (royler gracie lineage

) but i dont like the way eddie plays london. i think he plays it too flat on his back, if more than one shoulder is on the ground i would play something else. this is probably because eddie has badass flexibility and can pull it off though haha. the reason i only play williams guard (what i call the position) on one shoulder is for guard retention and offensive ability, if you think about it, most people can stretch their legs quite well in front of them compared to stretching your legs out sideways, so for me to attack well with omoplatas or triangles/reverse triangles etc i want to be on my side. and as far as guard retention i dont worry about the cartwheel or other passes (more in a bit!) im more worried about being smashed flat and having the opponent lawnmower pull out his overhooked arm, leaving me with a crappy/useless positon (especially when strikes are involved).
now for the cartwheel, i notice alot of people commenting on the low single in the above vid (which i agree with, my wrestling sucks too

) and disregarding the see-saw, shawn shows 2 techniques people! but you should really watch this video for excellent cartwheel counters,
http://www.youtube.com/watch?v=ovljbfZnoX4 btw rene dreifuss's rat guard series is excellent and well worth a watch, and another staple of my game! and the rat guard blends very well with london/rg techniques.
i am currently putting a pdf together of all the london/williams guard techniques i know and use, its 20 pages so far and i have only talked about entries

so i would love to find out more on the 10th planet perspective on the london position for some ideas to add to the book and my own game

, there has been some great ideas so far!