My condolences to our esteemed UK forum users. Let's see, the law says here in TN:

39-17-1307. Unlawful carrying or possession of a weapon.

(a) (1) A person commits an offense who carries with the intent to go armed a firearm, a knife with a blade length exceeding four inches (4"), or a club.

The law is stated more lengthy and there are more conditions, exceptions, places where to and where not to, can and cannots

This says "with the intent to go armed," so I think common sense would dictate which scenarios would not be appropriate to carry a blade alot of the time.

BTW, LBJ was the last U.S. President to tote a pocketknife if the History Channel is correct.