Yes Adrian very astutely put.
The upcomming firearms review is expected to extend to air guns which could be modified above the the 6ftlb and 12ftlb limits.Rumours within the trade suggest that mechanisms will be required to be tamper proof to prevent people winding up the power.eg hardened pins limiting transfer port dimensions ,sealed regulators,after market sales of springs.
The most worrying suggestion is that having avoided paying compensation to self contained gas cartridge weapon holders by offering them the opportunity to apply for an FAC at £58 and cabinet at £100 that all the older guns which are not tamper proof may have the same thing done to them.ie if you want to keep it pay up.
Legalised theft really!