I'll make a side bet with anyone that all cops around the Parliament building will be armed in the future.
Don't bet: you could easily lose because to some minds, arming could appear to be submitting to threats! Britain, and London in particular, have had decades of violence and different forms of terrorism aimed their way; it's hardly new and yet the lessons remain doggedly "unlearned" not because they are not understood, but because of political dogma associated with the John Bull way of handling things.
(Partly, it might be associated with the observance of international rules, which is something that the Brits tend to do as governments, much to the surprise and even amusement of fellow Europeans who agree to every European rule but do their own thing regardless. Had the UK been as pragmatic, it might never have thought about Brexit and suicide. As the captains of industry tried to tell the lemmings, diving off the White Cliffs of Dover is not good for you. Did they listen? But now a huge number of City jobs is already on the move even before the red button has been touched. Anyone thinking that means only a few thousand highly-paid individuals is a little bit mistaken.)
I think that armed policemen should come in different stages: an initial lot with pistols that can be quickly pulled and discharged at close quarters - which might have saved that policeman's life - and the other type of weaponry, long-range stuff, that requires room to move, raise and aim, which strikes me as being about as useful for close combat as a rocket launcher. Not that I have a rocket launcher, of course. Carrying
both arms seems silly, too, for I think being a quick-draw artist saddled with even an additional light burp gun on a strap isn't going to make you very responsive any day soon. (Just think of yourself as carrying two cameras, one hanging in front of your chest with a long lens on it, the other in a pouch at your belt, and the picture comes into focus, even if you miss making the once-in-your-lifetime shot, if you see what I mean.) As for the attack being uexpected, all people in the vicinity where a policeman is required should be viewed as possible attackers. Dozing on the job and complacency run hand in hand, if they run at all, that is; no, I am
not stating the poor guy who was stabbed was dozing on the job.
But something in training is clearly wrong: it happens every day in Israel where armed security is attacked by knife and even by women; the level and reality of threat seems to be being overlooked in some way: are they all trained to be on the watch for people who resemble the targets on the range? Is the first flash of a diced headcloth key? I wonder if Texas border guards are trained to identify targets with black sombreros and moustaches?