"Welcome to the Heart of London" is the bold aspirational statement on large signs put next to the main roads into the Cities of London and Westminster and erected in the early 1990s. Generally these signs are hard to spot due to them being covered in a thick, dirty, grey layer of pollution covering the words, and usually overshadowed by heaving glutinous traffic jams of buses, taxis, and lorries. Londoner's often like to say "If this is the heart of London, I'd hate to see the lungs". Westminster City Council is currently debating whether to remove them.

Update: There is a lot less pollution and traffic since the introduction of the Congestion Charge. Good old Ken Livingston