Before we assume this nonsense is limited to Britain, I carry a nice 4" Gerber bolt action knife. Like Tamara, I use it to cut things. It is a tool.
It amazes me how often someone is struggling with some of the very hard plastic bubble wrap, or strapping tape, and, after I've helped them out by cutting what they couldn't handle with fingernails, they are horrified at the fact I carry a knife.
I point out to them that (A) it is a tool and (B) it just saved them a bunch of frustration and (C) it's perfectly legal.
Now, the thing I don't mention is that, if necessary, I could use it to cut something like an assailant's carotid, brachial or femoral, not to mention the odd hamstring. Provided, of course, I wasn't carrying a pistol.
Please bear it in mind: there are many folks right here in the U.S. of A. who fear ANYTHING that might be used as a weapon.
Blissninnies one and all. A pox upon them on either side of the pond.