Prince William and Kate Middleton briefly broke up in 2007 during their dating phase.
A rediscovered tape from a Princess Diana tribute concert in 2007 shows William and Harry introducing acts.
Judi James' analysis revealed William's awkward dad-dancing and Harry's straight-faced reaction.
Harry looks to be talking to his fiancée, Chelsy, while William encourages him to join in.
Kate was seated several rows back, likely due to the break-up.
Chelsy was the first to notice William's attention-seeking dance, which she brought to Harry's notice.
Harry's reaction was that of a teenager whose dad is shaming them during a party.
William seemed to be boasting to Kate about enjoying his freedom and having fun without her, but he wasn't suited to this kind of body language ritual.
This was likely a small swan song before settling down with Kate.