What rules do you want to change?
https://www.police.uk/pu/advice-crim...on-of-weapons/
My gut feeling is that knife crime is more likely to reduce through cultural change than through tinkering with legal proscriptions and sentencing guidelines. I doubt greater restrictions or tougher sentences will have an effect - they haven't in the past. When I was working for our local Council there was a low level arms race of knife carrying (and sometimes use) often where frightened kids carried a knife for what they thought was self defence, but ended up escalating incidents that might have been avoided. Hard to break the cycle of fear and violence - but we had some success working with community/gang leaders to make knife carrying appear a sign of weakness not strength.