Its the same technique that guy used with the double decker bus a couple of weeks back.
It may be more comfortable that it looks Boogsy, some of the more complicated harnesses also have leg sections that can easily lock into place if you lift your legs high enough first so its no different that sitting in a chair.
I used a lot of magic tricks back when I was a student nurse working on a kids ward. There was always something special about the looks in their eyes when I'd levitate or make something appear out of thin air. It didn't matter what they were in for, how ill they felt or how nervous they were about getting injections or going in for surgery, whenever I'd start performing tricks at that point none of it mattered to them.