Original report said it, "caused a stir among fellow restaurant diners" which would suggest non-club people were present.
So, in your view, "somebody" spoke to the Daily Mail, might've been a staff member or a member of the public, but the person chose not to be named or even directly quoted.
You don't know who they are but your source says the noise caused was ear shattering, and he's been assured of this! He/she's told you more but you can't give details because you don't want to make it public information, in case there's repurcussions; but the information you've already divulged is OK, less repurcussive repurcussions as a consequence of that I guess.