Well, up until the 20's guns were exactly the same as a loaf of bread or an arm chair: no restrictions at all.
Then the government got concerned over left-wing groups, some of them armed, who might cause a revolution, like in Russia. A certification system was introduced where you would have to pay a fee at the post office to purchase a gun and this would be kept on record.
Over time this become more elaborate, eventually evolving into the system we know today with the need for 'good reason', background checks, the need for referees, long waiting times, maximum ammount of ammunition and so on. These things were often not laws, but guidelines and policies so never got attention until it was too late. And even when they did or when they were laws, so few people owned guns that few people were bothered by it. Britain was tamed with bows and arrows long before firearms were invented, unlike America, so there was no history and tradition of gun ownership amongst ordinary people. The odd person might have a derringer or something, ex-army types might have a .22 rifle, and farmers and the aristocracy, maybe the odd bar-keep, had shotguns but that was about it.
Back then, people had enough trouble putting food on the table, let alone worrying about buying a gun.
Well, in 1945 the Home Office decided that self-defence (preservation of freedom etc) would no longer be a 'good reason'. Up until then, any reason was good enough really, but afterwards only things like hunting and target shooting were valid.
This decision was made in secret, it was not a law but a guideline for police to follow. It only became public in the 1980's.
So, we never realised that guns for the express purpose of self-defence were gone. They just faded away.
This way, people lost all empathy with gun owners because hardly anyone knew one or was one.
Constant media and government propoganda finished the job. We're relentlessly pounded with stories and articles about how we need to stop people carrying knives and guns, how guns are evil and so on. It's all done so well. You'll have a newsreader announce "A man was arrested last night for the muder of such and such and police say they have found a gun in his house". You barely think to say "Hang on, so what if he has a gun? He has every right to! You don't announce 'a draw full of kitchen knives was found'!" and after people who don't really care have heard it 1000 times, they accept that guns = bad.
Now, the only people who carry proper knives are criminals (except maybe carpet fitters,, hunters, electricians etc) so knives are associated with criminals. People assume that if you were allowed to carry knives whenever you wanted, the criminals would have it easy as there'd be on law stopping them. I know it makes no sense but people don't think about it too hard and when they do, they just sput government rhetoric like 'it's be taken away and used against you' and 'the police will protect you'. Same for guns. With the exception of the small shooting community, only criminals have guns so that's what they're associated with.
