Not sure of the source, as I just googled it, but I was curious to see what happened in other areas that banned guns:
https://crimeresearch.org/2016/04/murder-and-homicide-rates-before-and-after-gun-bans/
Not really surprised.
That seems a silly argument.
The handgun ban after Dunblane was never intended to be about reducing the overall homicide rate - how could it, as handguns were not a significant factor in homicides in the first place, as very few people have them?
The point was simply to reduce the likelihood of another Dunblane, a single spree-killing by one of the small number of legal gun-owners.
(Personally I find it frustrating that such handguns were not banned after the Hungerford massacre, along with semi-auto rifles. If they'd done so it's very likely Dunblane itself would not have happened or would have been less deadly. It's as if the authorities will only ban the precise type of firearm that was used in the most-recent massacre).
So it's a bit silly to produce a graph purporting to show that the ban didn't do something that it was never intended to do, in a context where such guns were already vastly less common than the US.
What such bans do, it seems to me, is help bolster existing cultural traits by suppressing the growth of a gun culture.