The January transfer window might feel as if it has always been a fixture in the Premier League calendar, but in fact it first came into operation in the 2002-03 season.
Before the two-window transfer system as we know it today, top-flight clubs were allowed to trade players throughout the season up until March 31, after which point it was deemed that signing reinforcements could potentially undermine the integrity of the run-in.
The two-window system was devised by FIFA as a method of restricting players from merely moving clubs at will while still allowing them to be traded during set prescribed periods -- i.