Grealish had been at boyhood club Villa for the past 19 years, making 213 appearances, scoring 32 goals, and eventually captaining the team, after making his senior debut back in 2014.
But, after proving a pivotal member of the England squad that made it to the Euro 2020 final this summer, the 25-year-old attacking midfielder has made the step up by signing a six-year contract with the reigning Premier League champions after they paid his release clause.
The enormous £100m fee involved represents a new British transfer record, the second time City have held the record since their £32.5m deadline-day acquisition of Robinho from Real Madrid in 2008. By comparison, rivals Manchester United have held the record seven times, while Chelsea have claimed it twice in recent years.
Yet investing big hasn't always paid off for the clubs involved, with the top 10 of British record transfer fees featuring a mixed bag of players who instantly repaid the faith, those who took their time to get going, and those who have just flat-out failed to provide any value for money.
1. Jack Grealish: Aston Villa to Manchester City, 2021, £100m
Obviously, it's far too early to tell if Man City's massive outlay will prove shrewd, given Grealish has only pulled the shirt on once (and strictly for promotional purposes).
What we do know is that the midfielder was in fine form for England at Euro 2020 -- if only in fleeting cameos -- and appears ready, willing and capable of challenging at the next level.
Still, that's an awful lot of money for a player who hasn't scored a league goal since January (though he was injured for two months), and for a position in which City are already chock full of talent like Phil Foden, Bernardo Silva and Raheem Sterling.
Manchester United broke the world record (not just the British record) to sign a player who left join Juventus at the end of his contract for just £800,000 in compensation four years previous.
The fanfare was huge, the #Pogback promo campaign featured Stormzy, and Pogba seemed like exactly the kind of star name United needed to rejuvenate their stagnating squad.
It's fair to say Pogba has failed to fully convince everybody of his merits since, but the France midfielder has shown that he is a world-class player and a cut above on his day (which is roughly once a fortnight). Though, with his contract expiring in 2022, he may yet leave United in the coming weeks.
Many winced when Leicester centre-back Maguire left Leicester for Old Trafford for such a sky-high fee not long after impressing at the 2018 World Cup for England, though the gamble has since paid off.
The tough defender was quickly installed as club captain by Ole Gunnar Solskjaer, providing a rock-solid core to the most reassuring backline United have boasted in years.
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The one that got away for United. Lukaku never quite seemed to fit the mould at Old Trafford under Jose Mourinho and, despite mustering a decent goal return during his two seasons with the club (42 goals in 96 appearances), the Belgium international was allowed to join Inter Milan for around £74m in the summer of 2019 under minimal duress.
He has since fully restored his reputation as one of the most formidable forwards in Europe, scoring 64 goals in 95 games, with the Nerazzurri powering their way to a first Serie A title in over a decade last season. However, a return to Chelsea could be on the cards with the Blues reportedly putting forward an £110m offer last week which was rejected.
A world-class centre-back, Van Dijk barely seems to break a sweat while comfortably corralling the strikers of the Premier League and beyond.
With clubs seemingly now happy to pay as much for unflappable defenders as they do for 20-goal-a-season strikers, it's clear that Liverpool's eye-watering outlay to sign the Dutchman has since proven a shrewd investment as the Reds won their first Premier League title in two decades in 2019-20 and claimed the Champions League trophy the year before.
Indeed, Van Dijk's influence and importance to Liverpool was clearly underlined during his extended absence through injury in the latter half of last season, during which Jurgen Klopp's side systematically fell apart at the seams.
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After ripping it up in the Bundesliga for the past few years, United have gone big to bring Sancho to the Premier League after his youth career at rivals City saw him depart for £8m without making a single appearance in 2017.
His 50 goals and 64 assists in 137 appearances for Dortmund suggest that the England winger is exactly the kind of fleet-footed attacking catalyst Solskjaer was crying out for last season.
It doesn't really feel like Pepe has been at Arsenal for two years already, such has been the transient nature of the Ivory Coast forward's impact.
His first season passed him by with just eight goals in 42 games, but things improved greatly in 2020-21, when the former Lille star upped his contribution significantly. Pepe scored 16 goals in all competitions for the Gunners (the club's second-highest goal scorer behind Alexandre Lacazette) with his improved form being one of few positive aspects in a largely forgettable campaign for Mikel Arteta's mediocre mid-tablers.
However, he hasn't done enough to be considered anything less than a miss at this stage.
Kepa failed to ingratiate himself with the Blues faithful thanks to a string of unconvincing performances, exacerbated by an ill-advised display of insubordination during the 2019 EFL Cup final.
The goalkeeper stubbornly refused to be substituted during the final seconds of extra time in order to make way for penalty shootout specialist Willy Caballero, which led to an irate tirade from head coach Maurizio Sarri after the Blues' subsequent defeat to Man City.
The 26-year-old Spanish stopper has since been succeeded as first-choice by Edouard Mendy, who was signed for just £22m from Rennes in September 2020 and began his stint at the club by setting a record for clean sheets -- an utter bargain by comparison.
The Spain midfielder has hardly been electric for City but then again he was never meant to be, with Pep Guardiola routinely selecting the 25-year-old for his deep-lying, midfield-controlling presence.
Rodri also scored the winning goal in City's 2020 EFL Cup final triumph over Villa, so that's another tick in the plus column.
Havertz quickly attained wunderkind status at Leverkusen after scoring 46 goals for the club before turning 21, even famously having to miss several first-team games in order to sit his college exams.
The Germany playmaker has been a slow burner at Chelsea, but the momentum soon began to pick up as he found his feet -- scoring nine goals in his debut campaign for the Blues, the last of which just so happened to be a winner in a Champions League final.