I hate to say it because I'm generally against the idea of a police state but London could use "stop and frisk" for awhile until things calm down. It worked in NYC (of course it did lead to the unnecessary imprisonment of tradesmen who get arrested for carrying utility knives, and was pretty much a ticket for the NYPD to commit unfettered harassment on citizens).
That would probably reduce the immediate problem, but it is definitely a Faustian bargain; once the state has the power, it will not give it back, and it will increasingly ratchet up to an even bigger nanny state than the UK already has.
Guns, acid, trucks, knives, etc aren't the problem here. They are symptoms of the problem, and it's a lot easier to demonize these objects than to admit that some people are shit and monsters.
Acid attacks, truck attacks, knife attacks, grooming rape gangs... part and parcel of living in a society, but at least the British aren't racist.