Please confirm you are over 18
In the UK it is illegal to sell a knife to anyone under 18,
or to carry a knife in public without good reason
unless it has a folding blade with a cutting edge 3 inches long or less.
(excerpt from gov.uk website)

Knife purchases will only be accepted for customers to use within their business i.e. Fish / Meat Filletting or for Chefs, we may request proof of use for these items and reserve the right not to supply them if we have any doubt of their purpose.