My last trip to the UK I thought I was going to get SWAT called on me. I was working on the factory floor of a company that was installing some of our equipment.
We were needing to cut through a roll of some sort if Tyvek-like material - a common procedure for that equipment. They had a knife specifically for that job, but it was out of reach so I used my pocketknife (I brought it in checked luggage). The guys there all looked at each other and stepped back. They had a 6-8" folding knife, I had a 2" pocketknife. What made mine illegal was the locking blade.