A simple and useful informative guide to UK Knife Law as it currently stands in the UK.  We are NOT legal professionals and we are NOT offering professional legal advice in any way. this advice would be something that you would need to seek independently, This is a guide only to UK laws that surround the carrying and use of knives in the UK as we best understand them to be.
This guide is for information purposes only, and different parts of the country may apply different laws.  so be wise in your own judgement and use common sense.
The below information should not be relied upon in a court of law and encouragement to seek independent legal advice on any legal matters would be advised.
These items must be used responsibly and appropriately in the manner for which they are sold. 
UK Knife Law
The key is ‘Reasonable Cause’. You must have a genuine and appropriate reason for carrying a knife.

Folding Knives - UK knife law clearly states that any knife with a non-locking blade less than three inches in length is legal to carry in the UK. BUT, should you take this into an environment where you have no reasons to carry a knife, for example, a petrol station, sporting event, supermarket, etc, then you should expect to be prosecuted.

Fixed blade OR locking blade knives - of any length are not illegal to own or carry, IF you have ‘Reasonable Cause’ for doing so. This would include a chef carrying a roll of knives to and from work. OR, a fisherman needing a fillet knife, or a woodworker/ carpenter/bushcraft instructor traveling to and from work.  IF you are unable to show ‘Reasonable Cause’ then you could be prosecuted.
The responsibility is always down to the owner or person who is using or carrying the knife and it is their job to be able to provide sufficient evidence of ‘Reasonable Cause’ as to why they have a knife in their possession. Ignorance or forgetfulness is not a reasonable explanation.

You must always be aware of your surroundings, even a `UK-Legal` knife can be regarded as an issue in certain surroundings. Likewise a `Non-Legal` bushcraft knife can be regarded as acceptable if a legitimate use for the knife can be established.
When a knife is not being used, it must be stored in a correct safe manner and away from public view.
Some Knives which are illegal to own in the UK are:
Flick Knives, Switchblades, Gravity Assisted Knives, Automatic Knives, Push Daggers, Belt Buckle Knives, Cane Swords, Bali-songs or ‘Butterfly Knives’, Disguised Knives, Knuckle Duster Knives, Throwing Stars, Stealth Knives ‘Airport Knives’.
All of the above are also illegal to sell or import into the UK.
For more detailed information on UK knife laws please visit the links below
The Criminal Justice Act (Amendment)
The Knives Act (1997)
The Offensive Weapons Act (1996)
The Criminal Justice Act (1988)