I found this on the BKCG website
What You Can't Have ...
The following items are banned from sale within the UK (although if you already own one you may keep it, but not use it outside of your own property) ... Switchblades, automatics or 'flick-knives', gravity knives, balisongs or 'butterfly knives', push daggers, belt buckle knives, sword canes, or knuckle-duster knives.
You may not buy any knife designed to look like something else, for instance a knife which appears to be a pen, (and it doesn't matter whether the pen works or not, it's still a concealed weapon)!
What You Can Carry ...
The Criminal Justice Act (1988) said that you may carry a knife with a blade length of 3.0" or less as long as it is capable of folding. That means no fixed blade knives. But use your loaf - a knife has no place at a football match, in a pub, nightclub or school and becomes an offensive weapon in these circumstances in just the same way as a screwdriver, or any other innanimate tool.
But I NEED a Bigger Knife ...
If you wish to carry a larger knife then you must have 'reasonable cause'. That means that you must be able to prove that you had a genuine reason for carrying the knife.
You may carry a larger cutting tool if it is associated with your work (for instance a chef may carry a 9.0" butchers knife roll to and from work), or if it is associated with your sport, (for instance a fisherman may carry a 6.0" fillet knife, or a hunter may carry a 4.0" fixed blade hunting knife).
Don't forget it's there though. If you stop off in Tesco's for a can of beans on your way home take the knife off of your belt and secure it in your glove box, or your local Bobby will be unimpressed at your excuses.
Isn't Britain Great!