Alexander Isak signed for Liverpool from Newcastle for a British transfer record fee of £125m
It was the transfer window when spending by Premier League clubs went into uncharted territory.
Buoyed by the start of a record £6.7bn four-year domestic TV deal, and the extra revenue generated by newly expanded European club competitions, the top flight invested more than ever before this summer.
But while the unprecedented £3bn outlay, and the drama of a frenetic deadline day, undoubtedly fuels even more interest in the league, does it also raise concerns?
BBC Sport takes a closer look.
