I've been told (so this is second-hand from someone who follows such things closely) that the ban is on "edged weapons", which includes anything identified as sharp and pointy by the Powers That Be.
Let's also note that:
1. the British are "subjects," not "citizens," and so have no inalienable rights save those they are granted by their betters, and
2. that almost all the people from Britain I know (and there are a good dozen from all over the isles), find this agreeable since it's for the "common good." I hear that a lot from them. "For the common good."
O M G.........