the reality is there are a huge number of guns out there, there's no way you're going to make it impossible for a criminal to get a gun
It's not even difficult for criminals who want a gun to obtain on in the UK. Illegal guns are cheaper than legal ones, and a sizeable criminal market exists for them.
But almost no criminal in the UK routinely goes armed. When guns are used in crime, they are typically obtained for the specific crime, and discarded quickly once it has been committed. And even that is rare - most criminals prefer never to handle guns at all.
That's because simply possessing a gun without both a license, and a legitimate reason why it's not currently secured in an approved safe, is an invitation to arrest, and to severe penalties.
The system doesn't work by making it
impossible for criminals to obtain guns; It works by making it
undesirable for criminals to obtain guns.
And it does work.
When your entire approach to the problem is predicated on the false (and demonstrably stupid) premise that you can only stop gun crime by making illegal guns impossible to obtain, it becomes easy to prove that any given measure will be ineffective.
But when you look at actual and genuinely effective ways to reduce gun crime, you will discover that many of those measures are extremely effective, but are promoting a class of solutions that you haven't even considered.
When you tell legitimate gun owners that their weapons must be secured when not in use, you achieve two useful things that are unrelated to the diversion of firearms to the illicit market via theft: Firstly you eliminate a vast majority of accidental shootings, particularly by children; And secondly, you make it possible for any person found with a gun to be penalised simply for carrying it about without an immediate legitimate purpose.
Ultimately, this boils down to the central question around gun control: Do citizens have the right to own guns for their own protection against other citizens; Or is gun ownership a privilege reserved for responsible people, who have legitimate uses for these weapons that do not ever entail their use against humans?
As long as you pick the former over the latter, lots of people will die needlessly every single year.
Every developed nation in the world has picked the latter, except one; There's zero evidence to suggest that that one outlier has more liberty, less crime, or better public safety than the others - so empirically, that was a stupid mistake for that nation to make.
Basically, your nation has decided to kill large numbers of innocent people, in defence of a hypothetical benefit that cannot be demonstrated to exist at all. But lots of people both believe strongly in this hypothetical benefit, and care naught for the dead and wounded, so that's OK then.
The rest of the debate is just noise, intended to sweeten the bitter pill of realising that you have deliberately chosen an ideological position of pure faith that kills people, over the harmless and completely reasonable restrictions imposed in other countries to protect the public.