Six English teams are part a breakaway European Super League, but what do we know so far?
What has happened?
Twelve of Europe's leading football clubs have announced they have agreed to establish a new midweek competition, the European Super League, governed by its 'Founding Clubs'.
The proposal involves the clubs forming their own competition to rival the UEFA Champions League.
Which clubs are involved?
The Premier League's big-six clubs - Manchester United, Manchester City, Liverpool, Arsenal, Chelsea and Tottenham - are all involved.
AC Milan, Arsenal, Atletico Madrid, Chelsea, Barcelona, Inter Milan, Juventus, Liverpool, Manchester City, Manchester United, Real Madrid and Tottenham Hotspur have all joined as 'Founding Clubs'.
It is anticipated a further three clubs will join ahead of the inaugural season, which, according to the clubs, 'is intended to commence as soon as practicable'.
German giants Bayern Munich and Borussia Dortmund are not included and nor are French champions Paris Saint-Germain.
Why has this come about now?
The clubs say that "the formation of the Super League comes at a time when the global pandemic has accelerated the instability in the existing European football economic model. Further, for a number of years, the Founding Clubs have had the objective of improving the quality and intensity of existing European competitions throughout each season, and of creating a format for top clubs and players to compete on a regular basis.
"The pandemic has shown that a strategic vision and a sustainable commercial approach are required to enhance value and support for the benefit of the entire European football pyramid."
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However, Sky Sports News reporter Kaveh Solhekol says this has come about now for one reason, and one reason only.
"The reason it is happening now is because we have had a global pandemic, finances at the biggest clubs in Europe have been hit," he said.
"I keep saying it is about money, and if you look at the finances, a club like Man Utd playing in the Champions League, they make between £40m and £80m on a good year if they win it.
"If they play in this new competition, they get a cheque for £250m-£300m to begin with, then in the future they will get three times as much money a season as they get from the Champions League.
"You are looking at £200m-£250m in TV rights, they will be able to sell some of the rights to the games themselves on their own channels, the broadcast rights all over the world."
What does it mean for the Champions League?
If the Super League goes ahead, it would effectively rival and then hope to replace the Champions League.
Sunday's developments came just 24 hours before UEFA were due to discuss proposed Champions League reforms. The reforms were seen as an attempt to reach a compromise with the clubs in favour of a breakaway competition by offering them more matches.
The reforms were planned to come into effect in 2024, expanding the Champions League to 36 teams, adjusting the format and increasing the number of matches from 125 to 225.
The reforms were intended to favour the clubs central to the Super League and even included a safety net of four qualification spots for clubs based on their past performance in European competition, should they miss out on qualification through domestic competition.
But it seems the reforms do not go far enough for Europe's biggest clubs.
What would the format be?
The Super League website reads: "The Super League is a new European competition between 20 top clubs comprised of 15 founders and five annual qualifiers. There will be two groups of 10 clubs each, playing home and away fixtures within the group each year.
"Following the group stage, eight clubs will qualify for a knockout tournament, playing home and away until the single-match Super League championship, in a dramatic four-week end to the season.
"Games will be played midweek, and all clubs will remain in their domestic leagues."
In their statement, the clubs themselves have outlined the format in three stages:
- 20 participating clubs with 15 Founding Clubs and a qualifying mechanism for a further five teams to qualify annually based on achievements in the prior season.
- Midweek fixtures with all participating clubs continuing to compete in their respective national leagues, preserving the traditional domestic match calendar which remains at the heart of the club game.
- An August start with clubs participating in two groups of ten, playing home and away fixtures, with the top three in each group automatically qualifying for the quarter-finals. Teams finishing fourth and fifth will then compete in a two-legged play-off for the remaining quarter-final positions. A two-leg knockout format will be used to reach the final at the end of May, which will be staged as a single fixture at a neutral venue.
Would the league be a 'closed shop'?
One of the immediate points of criticism - if not the major point of criticism - around the proposal is that only five of the clubs in the 20-strong competition would enter based on 'sporting achievement'. As outlined above, the other 15 clubs, the so-called 'Founding Clubs', would have their participation guaranteed.
Juventus chairman Andrea Agnelli has talked up the enormity of the Founding Clubs. "Our 12 Founder Clubs represent billions of fans across the globe and 99 European trophies," he said.
While there unquestionably powerhouses involved, as a collective, the 12 European Super League clubs are neither the dozen most historically successful, biggest earners, or current top-performing clubs.
Four have never won a European Cup or Champions League.
AC Milan have a smaller revenue than Crystal Palace and Sheffield United.
And five of the teams weren't involved in this season's Champions League knockouts, with two more failing to make it beyond the last 16.
How would the league be financed?
About $5billion has been committed to this new project by the American bank JP Morgan.
In their own announcement, the breakaways clubs state 'The Founding Clubs will receive an amount of €3.5 billion solely to support their infrastructure investment plans and to offset the impact of the COVID pandemic.'
What happens next?
Going forward, the Founding Clubs say they "look forward to holding discussions with UEFA and FIFA to work together in partnership to deliver the best outcomes for the new League and for football as a whole."
What has the reaction been?
The plans have prompted widespread condemnation, with Sky Sports pundit Gary Neville, speaking before the announcement on Sunday night, labelling the English clubs involved a "disgrace" and calling for them to be sanctioned by the Premier League.
Governing bodies and leagues across Europe are viewing the proposal as an attempted power grab.
The Premier League released a statement saying a super league would "destroy" the premise of open competition.
"Fans of any club in England and across Europe can currently dream that their team may climb to the top and play against the best," said the statement. "We believe that the concept of a European Super League would destroy this dream."
UEFA was similarly critical in a joint-statement with the English Football Association, the Premier League, the Spanish FA, La Liga, the Italian FA and Serie A and threatened to ban participating clubs from their domestic competitions.
"We will consider all measures available to us, at all levels, both judicial and sporting in order to prevent this happening. Football is based on open competitions and sporting merit; it cannot be any other way.
"The clubs concerned will be banned from playing in any other competition at domestic, European or world level, and their players could be denied the opportunity to represent their national teams."
Even Prime Minister Boris Johnson has had his say, tweeting: "Plans for a European Super League would be very damaging for football and we support football authorities in taking action. They would strike at the heart of the domestic game, and will concern fans across the country.
"The clubs involved must answer to their fans and the wider footballing community before taking any further steps."
Will the Premier League, UEFA, FIFA and others try to stop this?
The Premier League held a virtual meeting on Tuesday without the 'Big Six' clubs, chaired by Premier League CEO Richard Masters.
On the same morning, an Everton statement slammed the "preposterous arrogance" of the breakaway six, with some other clubs showing their disproval via statements or social media.
Aleksander Ceferin, the president of UEFA, has slammed the ESL concept and the 12 sides involved, strongly condemning the "disgraceful" proposals for a new European Super League as a "spit in the face of all football lovers".
The head of the European governing body also confirmed any players featuring in the European Super League will be banned from the World Cup and European Championships, with bans for the latter competition being sought "as soon as possible".
FIFA and the European Club Association (ECA) have also criticised the creation of a breakaway competition.
Prime Minister Boris Johnson vowed the government will do everything it can to make sure the new European Super League "doesn't go ahead in the way that it's currently being proposed", as one 'Big Six' board member says there is a "nuclear war" in football.
How realistic is this?
This does feel significant, both for the future of English and European football.
We have been here before - namely Project Big Picture - but what feels different this time is the level of planning.
The furious reaction from the Premier League, UEFA and other European leagues signifies just how much this threatens the integrity of domestic and European leagues.
Clubs would need the approval of the associations, who govern the domestic competitions, to join an unsanctioned breakaway league.
"I cannot envisage any scenario where such permission would be granted," said Premier League chief executive Richard Masters in a memo to all 20 Premier League clubs.
What would the ramifications be?
Potentially huge. Under Premier League rule L.9, which all 20 clubs sign up to, clubs must obtain 'prior written approval of the Board' if they wish to enter to anything other than the Champions League, Europa League, FA Cup, FA Community Shield, Carabao Cup or any other competition sanctioned by the county association.
Any player whose club agrees to join an unsanctioned competition risks not playing in any UEFA or FIFA competition, including the European Championships and World Cup.
In January, FIFA had said that a breakaway league would not be recognised and that "any club or player involved in such a competition would as a consequence not be allowed to participate in any competition organised by FIFA or their respective confederation."
In a special podcast, Jasper Taylor sums up a seismic 24 hours in football after Arsenal, Chelsea, Liverpool, Manchester City, Manchester United, and Tottenham agreed to join a breakaway European Super League, along with six other teams.
The reaction has been swift, damning, passionate and emotional to say the least. Hear from Gary Neville, Kaveh Solhekol, Bryan Swanson and more....
Gary Neville gives his opinion on reports of plans for a breakaway European Super League. Sky Sports has contacted the clubs concerned for their responses.