OK the laws here are pretty harsh, you can not carry any knife anywhere for any reason, period.
Not fixed, nor folding, nor locking and certainly not flicking, gravity, or balisong type knives, I suspect that assisted are also illegal.
Doulbe edged and push daggers are also illegal-attempting to bring them in in his/her luggage may get you a free return ticket home.
So saying all that you are allowed blades in the home, and if you are on a hunting trip, bush walk, farmers, camping etc, then no one would blink if you had a sak, leatherman or small hunting knife of some sort, carryng a machete, rambo style knife or a kukri would not be a good idea though.
Further though, and here is a grey area, whilst the police can and will lock you up for walking around with a knife (or even a screwdriver - I kid you not) on your person, if you have a very good reason, you may get away with it: note though, a good reason is something like "I work at the docks, cutting ropes/string and if i leave it at work someone will pinch it-if you have proof thats where you work you may get away with it IF you are on the way home/going to work-will not work at the pub.
Please note : " I carry it for self defence" will end you up in the cells so fast that your head will spin and the knife WILL be destroyed.
These laws may seem harsh, we are not allowed guns either, they are the laws and if you come to our country then you have to accept out laws, otherwise you should not come here.
So saying all that it is still possible to carry knives, bad guys often carry knives, and if you know how to use one then by all means carry one if you want to break the law (I have to say that because of my job).
Ginving your friend a good pair of running shoes may be a better idea though!
You can buy some knives here-they are just stupidly expensive, but its possible-if you want them to have a knife give them a sak or a leatherman, if you want them to have a SD knife, and they know how to use it, maybe give them a spyderco or a Zero tolerance flipper, or a emerson, something small and fast to draw.
I would not give them a fixed blade unless they are going to be working/living on a farm, or as a guide or something like that.
Hope this helps...