"We received a visit from a member of staff from Clarence House asking very in-depth questions about hair loss," says my clinic source.

"He said it was for a VIP who he couldn't say much about but, from the detail he did provide, it seemed very likely he was talking about William."

The Prince regularly wears a baseball cap to hide his thinning thatch. A chum of Wills adds: "He is very sensitive about it --he is thinning quite badly."

A spokesperson for Clarence House last night insisted no enquiry was made to the clinic on behalf of the Prince.