No guarantee it would. Some may choose to keep illegally. Plus, if someone is hellbent on committing this kind of thing they will buy a gun illegally or just drive their car down a busy street. Granted its harder but the numbers so low as it is.
Yes. Nobody can know how many illegals guns there are, but I've seen a police estimate of around half a million, and we need to be aware that criminals seem to be able to buy them quite easily.
And we also need to be aware that very nearly all gun crime involves illegal guns.
And we also need to be aware that nothing whatever that successive governments have done over the years has reduced the amount of gun crime in any way, which supports my argument (and that of many others) that making life even more difficult for legitimate shooters won't do anything to improve public safety.
So, where do all of these illegal guns come from? Ignoring for the moment the ones that are smuggled into the country, adapted from airguns or blank firers, made with a 3D printer or on a lathe, I know of a couple of different origins. Firstly, there are "war souvenirs" brought back by servicemen. I remember that my own father had a Lee Enfield rifle when I was a small child, He had been a sniper in the British army and I don't think that he could have held it legally because he had left the army before I was born. I've no idea what happened to it. And when he died and I cleared out his home I found a fully functional British army revolver. He wasn't an officer and would not have been issued with it, so I can only guess where that came from. And that doesn't even count as a gun because it has an obsolete calibre, .455.
And when I was at school in the 1950's there were plenty of guns, of all sorts, I even remember one kid taking a handgun to school and showing off with it, it was pretty common back then.. What happened to all those old guns which, unless allowed to rust away, will still be fully functional?
And then there are the shotguns, which this thread is concerned with. When I bought my first shotgun I bought it by mail order from Littlewoods, anyone could have one back then and the only licence needed was bought from the post office and cost the equivalent of 50p - just like a dog licence, no record or who had bought it. I think that actual shotgun certificates were introduced in 1986. They didn't include a photograph, we just walked into the police station and filled in a form. I remember the desk Sgt asking me whether I had been in trouble with the police and when I said "No" he stamped the form, signed it and handed it to me . . . So, did everyone who held a shotgun before that get a certificate? I doubt it, many wouldn't have known, pre-internet, that certificates had been introduced and many wouldn't have bothered anyway. Many of those people will be dead now, what happened to their guns? Back then, they didn't even have to be locked up.
And I remember a registered firearms dealer friend telling me that every now and again he would find all sorts of guns dumped on his doorstep. Presumably, they were from people who held them illegally and who didn't want to bother going to the police with them, but there is an obvious risk that criminals may check gunshop doorways before the dealers arrive at work.
I heard something on the news last night to the effect that Home Secretary Priti Patel has announced some new rule, I don't know what it is yet but I doubt whether even a competent Home Secretary could come up with something that's actually useful so quickly, but it may make her popular with the ignorant.
The only change that I would personally make is to completely ban all imitation firearms, including the airsoft and pellet air pistols that are almost exact copies of real guns - if a criminal points one of these at anyone (including a gun expert) it's impossible to tell them apart from the real thing. Why are they allowed to look real?