CNN  — 

With plot lines that would make even the writers of Game of Thrones scratch their heads, the 2021 European summer transfer window may very well have been the best one ever.

Not only did the unthinkable of Lionel Messi leaving Barcelona happen – moving to pastures new at Paris Saint-Germain – but his long-time rival Cristiano Ronaldo also secured a remarkable transfer, returning to Manchester United in an incredible U-turn after it had been widely reported he would be joining bitter rival Manchester City.

If arguably the two greatest players of all time moving in the same transfer window wasn’t enough, ‘Deadline Day’ on Tuesday also saw Antoine Griezmann return to Atlético Madrid on loan from Barcelona, while Atleti’s Saúl Ñíguez swapped the Spanish capital for the English one, joining Chelsea on loan until the end of the season.

Manchester City’s $138 million purchase of England star Jack Grealish, United’s signings of Raphael Varane from Real Madrid and Jadon Sancho from Borussia Dortmund, and Chelsea’s $135 million acquisition of Romelu Lukaku from Inter Milan helped push the Premier League’s spending to more than £1 billion ($1.37B) for the sixth summer transfer window in a row, according to Deloitte.

READ: $138m Jack Grealish transfer shows it’s business as usual for English Premier League’s elite

Manchester United fans hold up a cardboard cut out of Cristiano Ronaldo during their Premier League match at Wolves.

Such were the hectic final days of the transfer window, there were several high-profile signings that took place earlier that were somewhat overshadowed.

Not only did Real Madrid lose Varane, it also lost its other central defender as captain and talisman Sergio Ramos departed for PSG on a free transfer.

However, Real did some equally impressive business of its own with the free signing of Bayern Munich’s David Alaba and the Deadline Day purchase of 18-year-old Rennes midfielder Eduardo Camavinga, one of the most highly-rated prospects in European football, for a veritable steal of $36.6 million and $10.6 million in add-ons.

As it aims to bolster its ranks following Alaba’s departure, Bayern completed the signing of RB Leipzig’s sought-after defender Dayot Upamecano for a reported $50 million.

Meanwhile, Barcelona tried to adapt to life after Messi with the Deadline Day loan signing of Sevilla’s Luuk de Jong, along with the previous additions of Memphis Depay from Lyon and Sergio Aguero from Manchester City.

READ: Spending on international transfer fees nearly tripled in 10 years, FIFA says

Harry Kane looked set for a move away from Tottenham all summer.

However, the window was almost as much about the players that didn’t move as those that did.

Perhaps the longest-running saga was that of Harry Kane, who was reportedly courted by Manchester City all summer but ultimately remained at Tottenham after chairman Daniel Levy refused to sell his most prized asset.

There was a similar story that played out in the French capital, as PSG striker Kylian Mbappé was reportedly denied a move to Real Madrid after the French club failed to respond to a Deadline Day bid in excess of $200 million from the Spanish giant, despite the fact that the young star can move away from PSG for free in the summer of 2022.