UK Legal Carry explained.
https://www.youtube.com/watch?v=DbHMBEtFJK8Do not ever show off your knife (even if UK legal) in Public in the UK to folks you do not trust. They may call a Policeman.
A lot depends on your demeanor, attitude, age and how well your dressed.
The Police in Scotland for example are looking for 'Bams',

There is a big difference between the city and countryside cop.
https://www.youtube.com/watch?feature=player_detailpage&v=uZErqrwkbMM#t=600i.e. Countryside Policing
https://www.youtube.com/watch?feature=player_detailpage&v=YLnv7gC3Or0#t=800