"And yet, despite the multiplicity of times we've done it, it is still a funny, exultant, true thing - where for a short time you turn into something else and fly; where you stop fretting and wanting, and are simply alight with joy - and all while never venturing beyond the walls of your room. And I would put our continued success down to one simple thing. At the end of every tumbling session, one of us will turn to the other and say, "Thank you very much. That was very pleasant. Very pleasant indeed. My dear, I am much obliged to you."