Complex sentence: According to the London Metropolitan Police Service (MPS), the original Metropolitan Police Commissioner's office at 4 Whitehall Place backed onto Great Scotland Yard, and the shortened version of street's name came to be used generally as a metonym for the MPS headquarters.
Split into simpler sentences: According to the London Metropolitan Police Service (MPS), the original Metropolitan Police Commissioner's office at 4 Whitehall Place backed onto Great Scotland Yard. Over time, the shortened version of street's name, Scotland Yard, came to be used generally as a metonym for the MPS headquarters.