Sentence:  It is one of the ironies of capital cities that each acts as a symbol of its nation, and yet few are even remotely representative of it. London has always set itself apart from the rest of Britain — but political, economic and social trends are conspiring to drive that <WSD>wedge</WSD> deeper. 
Meaning of the word marked with <WSD> tags:  Something that creates a division, gap or distance between things.