I don't know how it works in E&W and NI. In Scotland there is a potential 5 year prison sentence for carrying a knife (or even an object fashioned like a knife). Knife related crime in Scotland has dropped significantly over the last decade.
No idea what happens with regards to chefs carrying knives. There are lots of other things you could carry that have the potential to be weapons. I don't know if similar penalties exist for those.
Good knives are the most important kitchen tools.