These spikes are embedded every couple of feet in the hand-rails of a staircase at Highbury & Islington station in London, presumably to prevent kids (or adults) sliding down them. They’re not especially sharp, but would bruise someone pretty badly.

Note that there are also additional stainless steel hand-rails – this staircase may have replaced an escalator, and the rubberised rails may be the original escalator ones, with the spikes added much more recently.