William and Harry introduced acts at a 2007 Princess Diana tribute concert on an unearthed tape.
While encouraging Harry to join in, William appears to be conversing with his fiancée, Chelsy.
Chelsy was the first to notice William's attention-seeking dance, and she immediately informed Harry of it.
William seemed to be gloating to Kate about his freedom and enjoying life without her, but he wasn't ready for this body language ritual.