And thus begins a story that may take a few years to completely play out and may end up changing the way that UK Law considers / defines certain objects and their capability to do harm.
At what point does a 3D-printed object 'become' a bullet or a part of a gun - what defines its 'intention' as an object (and thus its potential capability to do harm)? The object printer's intent / proof of that intent must surely also play a part? Will it one day be a chargeable offence to merely possess a 3D / CAD file for something that might or might not (in an expert's opinion) become just one part of a potential weapon? You can see how this might easily drift into the realm of Futurecrime / precog Crime.
And, really, have senior UK police officers (in the GMP or otherwise) seriously never considered the ramifications of / potential for 3D-printed weapons? Seriously, not ever? Not even in private?
I find that really hard to believe.
"What is a gun?"