Since I usually carry around a pocket knife (as a utility tool), I thought it would be worthwhile researching the relevant laws to know where I stand. Basically, it seems that you cannot carry a knife for the purposes of self defence, however if you have a reasonable excuse (such as utility tasks, work or other lawful activity requirements) then you are allowed to carry a knife – no size restrictions. However, you must not carry/use/act with the knife in such a way that a “reasonable person” would be scared/concerned.
Here’s the two relevant acts/regulations that I found:
Weapons Categories Regulation 1997
Page 8, Section 7A Category M weapons (c),
any knife so designed or constructed so as to be used as
a weapon that while the knife is held in 1 hand, the blade
may be released by that hand;
The weapons category regulation, defines what is considered to be a category M weapon. My reading of this is that a knife is only a category M weapon if it is a knife that is designed as a weapon. If not for requirement for intended use as a weapon, then I believe a stanley knife would fall under this category. In the case of a linerlock type knife with opening studs, it is probably a bit grey, however if it was argued in court they’d need to show that it was designed or constructed as a weapon – something which I think would be pretty hard to do. (this is not for assisted openers or other such banned knives)
Weapons Act 1990
Page 74, Section 51 Possession of a knife in a public place or school
(1) A person must not physically possess a knife in a public place
or a school, unless the person has a reasonable excuse.
(2) It is a reasonable excuse for subsection (1) to physically
possess a knife—
(a) to perform a lawful activity, duty or employment; or
(b) to participate in a lawful entertainment, recreation or
(c) for exhibiting the knife; or
(d) for use for a lawful purpose.
Example for subsection (2)(a)—
1 A person may carry a knife on his or her belt for performing work
in primary production.
Examples for subsection (2)(b)—
1 A scout may carry a knife on his or her belt as part of the scout
2 A person may carry a knife as an accessory while playing in a pipe
3 A fisher may carry a knife for use while fishing.
Examples for subsection (2)(d)—
1 A person may use a knife to prepare or cut food at a restaurant in a
public place or when having a picnic in a park.
2 A person may carry a pen knife or swiss army knife for use for its
normal utility purposes.
(3) However, it is not a reasonable excuse to physically possess a
knife in a public place or a school for self-defence purposes.
(4) In deciding what is a reasonable excuse for subsection (1),
regard may be had, among other things, to whether the way
the knife is held in possession, or when and where it is held in
possession, would cause a reasonable person concern that he
or she, or someone else in the vicinity, may be threatened or
The weapons act, covers when it is allowable to carry a knife. Points 2a, b and d i believe are the relevant parts. So, a reasonable excuse would be if you use it for your work (stripping wires, cutting rope, opening packages etc) or, as per the example, for “normal utility purposes”. Note that this says nothing about knife types – as long as the knife doesn’t fall into a weapons category (which, if used for lawful purposes as above, it doesn’t), then it says nothing about what is or isn’t covered. So, no limits on blade length, or limits on fixed blade knives or their size. Point 4 however, does mean that if you carry around a scary looking knife you could be in trouble.