Please correct me if I'm wrong, I believe that in your UK legal environment, anything which is designed as a "weapon" in its primary purpose, is probably going to get unwanted scrutiny. It is probably better to use your fireplace poker, golf club, or walking stick.
100 years ago walking sticks were commonly used as defensive weapons. Anyone who was ever trained in use of a riot baton or truncheon could make good use of the cane.
In the US I would not want anyone suspicious to get close enough to touch with a cane, that is already considered danger-close as discussed here:
http://www.policeone.com/edged-weapons/a...id-Part-1/
Links on use of riot baton. In most places a long baton is considered a deadly weapon and is regulated, however, these techniques could be used with a cane or walking stick.
http://www.telegraph.co.uk/news/newsvide...ation.html
http://www.armystudyguide.com/content/SM...riot.shtml
http://www.armystudyguide.com/content/SM...gres.shtml