The January transfer window is official open, giving all 20 Premier League clubs the chance to bolster their squads for the second half of the season. The winter transfer window promises exciting, unpredictable signings and departures across the English top-flight.

We are already past the first week of the midseason business period for European soccer clubs, but when is transfer deadline day?

Barcelona, Chelsea and Liverpool are among the teams that have been involved in the most expensive transfers of January window history.