Being the good newshound that I am, I asked ACPO whether he was actually a member of the Firearms and Explosives Licensing Working Group (FELWG). I don't recall seeing Squires' name in any of their public minutes and so for him to tout himself as an ACPO adviser would be naughty if it wasn't true.
I quote the reply in full, less the press officer's name:
Dear Gaz –
I have consulted with the national policing leads both for firearms policing and firearms licensing and neither of them are aware of Prof Squires – he is certainly not a member of FELWG. He has done work for the Centre for Crime and Justice Studies which, conceivably, found its way onto the desks of members of FELWG, but he is not known to us as a direct advisor.
All good wishes,