anything that locks and/or is over 3" (if think??) is (by British law) illegal.
Here ya go!
"Basic laws on knives
It is illegal to:
sell a knife of any kind to anyone under 18 years old (16 to 18 year olds in Scotland can buy cutlery and kitchen knives)
carry a knife in public without good reason - unless it’s a knife with a folding blade 3 inches long (7.62 cm) or less, eg a Swiss Army knife
carry, buy or sell any type of banned knife
use any knife in a threatening way (even a legal knife, such as a Swiss Army knife)
Lock knives (knives with blades that can be locked when unfolded) are not folding knives, and are illegal to carry in public without good reason."