Thank you very much to all those who chimed in.

On one hand, I'm relived by Chaosmagnet's and Mr Ritter's (a true authority on the subject!) assurances that I won't have problems on the streets with a simple penknife in my pocket.

On the other hand, I think it would be a real nuisance to plan beforehand whether or not I should carry the knife with me according to the presence of absence of security checks in the places I plan to visit for the rest of the day.

In this respect, I'm inclined to follow the advice of Haertig and Phaedrus and just be on the safe side.

Unfortunately, we live in a society (and I count my home country in the fold as well) where laws and regulations can have so many different interpretations and applications, every one of which can result in very different outcomes to those caught on the wrong side of the authorities.

It's very sad, but on certain occasions you may be inclined the refrain to do something, even if it is totally in your right to do so, just to avoid the stress and potential harassment that may ensue...