It would be classed the same as pepper spray in the UK (a "noxious chemical").
The skunk lock and similar products that use a malodorous chemical are illegal in the UK for this reason.
There are "self defense sprays" sold in the UK and some other countries that just contain a dye, no irritant or malodorous substance, but even those are legally questionable at best - just there's been no case law yet that I'm aware of.
That all seems a bit excessive doesn't it? Does that mean you can't carry a pocket knife either? I would be lost without my Leatherman or at least a swiss army knife.
As for knives in the UK: so long as the blades under 3 inches long, and it is a non locking folding knife, it is legal to carry in public (with some exceptions).
Any knife longer than 3 inches, or any knife with a locking blade, cannot be carried unless you have a good reason (eg: going to/from work, etc).
You likely will have to argue this reason in court if the police officer is a cunt, and most of them are cunts when it comes to having common sense around blades.
Fixed blade knifes of any length require a "good reason" to carry.
A lot of coppers in the UK are ignorant as fuck too, and will confiscate your folding, non locking, sub-3 inch Swiss army knife requiring you to jump through burning hoops, wade through an ocean of piss, and sacrifice a virgin goat at midsummar to get it back.
At the other end of the spectrum my kid can walk around with a machete and be perfectly legal, but her school library can't have V for vendetta. Is there anywhere that doesn't nanny about access to ideas or "weapons" (I'd rather use an umbrella as a weapon than a Leatherman if it came to it).
In defence of the police officers, you are probably dealing with similar level of anxiety as soldiers. I imagine a high number of them have had to deal with a knife incident and just because you’ve got a taser, some training and some backup doesn’t necessarily mean it’s going to end well for you. There are quite a few reports of people (especially large blokes like rugby players) who can shrug off a taser and go on a rampage. It famously took 20 police officers to arrest Eddie Hall and that was before he became a professional strongman.
I’ve heard the expression “don’t go into a knife fight and expect to come out uncut”. As in, even if you win, there’s a high likelihood you’re going to have slash wounds on some part of your body somewhere. Yes a bit of common sense should be in order but I can also understand why they want to be very strict about these things. Having to deal with a knife fight and the aftermath probably isn’t a great day at work.
The problem is, if the officer doesn't believe your reason is good enough, you end up having to go to court over it - which is expensive, and you may well lose and catch a custodial sentence.
I can't really overstate how ridiculous the UK's laws around knives are.
Even tradesmen with glaringly obviously valid reasons to carry knives are recommended to lock them securely in a toolbox while not at the jobsite to avoid prosecution.
It would be classed the same as pepper spray in the UK (a "noxious chemical").
The skunk lock and similar products that use a malodorous chemical are illegal in the UK for this reason.
There are "self defense sprays" sold in the UK and some other countries that just contain a dye, no irritant or malodorous substance, but even those are legally questionable at best - just there's been no case law yet that I'm aware of.