In the Uk how legal is it to carry in public a 2 or 3 inch knife or blade?

I am currently working as a Door Steward or Bouncer if you like.I come across all sorts of people in my work.I can handle myself when it comes to knuckle fighting 3 to 1 but say 6 guys id have a problem beating.I have no problem using a pocket knuckle duster/bottle opener that i keep around my neck at all times.From a legal stand point i would like to know the legalites of carrying a small 2 inch or 3 inch knife in the uk such as a boot knife or something similer.I have been a Bouncer for 8 years and these days some people just wanna be nasty so it's always nice to be nasty back sometimes also it's good protection and peace of mind for a guy in my kind of work.10 points no problem to the best & most informative answer thanks.