Chelsea boss Jose Mourinho has stunned the world of football by leaving Stamford Bridge by mutual consent.
Mourinho's position was the subject of continual scrutiny last season
The decision comes after the club held a crisis meeting to discuss the indifferent start to the new season.
Mourinho, 44, joined Chelsea in June 2004 and led them to the Premiership title in each of his first two seasons.
But his relationship with Blues owner Roman Abramovich grew increasingly troubled and he quit despite having three years left on his contract.
Former Israel coach and Chelsea's director of football Avram Grant will take over from Mourinho, whose compensation package is still being agreed.
BBC Radio 5live football correspondent Jonathan Legard understands Mourinho texted senior players, including skipper John Terry, to tell them he was leaving.
Meanwhile, Peter Kenyon, the club's chief executive, Bruce Buck, the chairman, and Abramovich's key aide, Eugene Tenenbaum, were called to an emergency meeting at Stamford Bridge last night to discuss the emerging crisis.
A statement on the Chelsea website confirmed: "Chelsea Football Club and Jose Mourinho have agreed to part company today (Thursday) by mutual consent."
MOURINHO'S CHELSEA RECORD
2 June, 2004 - Appointed manager
27 February, 2005 - Wins Carling Cup 3-2 v Liverpool
30 April, 2005 - Beat Bolton 2-0 to win Premiership title
4 May, 2005 - Signs new five-year contract
29 April, 2006 - Beat Man Utd 3-0 to win Premiership again
27 February, 2007 - Beat Arsenal 2-1 to win Carling Cup
19 May, 2007 - Win FA Cup by beating Man Utd 1-0 at Wembley
19 September, 2007 - Leaves Stamford Bridge
Many of Chelsea's staff and players had been enjoying a relaxing evening at a Fulham Broadway cinema last night as they watched a screening of "Blue Revolution" - a new documentary about the Abramovich years.
But senior players such as Terry and Frank Lampard were absent and the remainder, except a reluctant Shaun Wright-Phillips, refused to talk to the media.
Mourinho also attended the evening but ignored the waiting media and looked decidedly glum.
The Portuguese made a massive impact at Chelsea after joining them from Porto, whom he guided to Champions League glory in 2004.
Last season, the Blues finished runners-up to Manchester United but won both the FA Cup and Carling Cup, a trophy they had also collected in 2005.
Mourinho's achievements also saw him voted as Premiership manager of the year in 2005 and 2006.
He's a very individual man and he thinks he should be the power at the club
However, the Champions League trophy eluded the club and this season's campaign started with Tuesday's shock 1-1 draw at home to Norwegian side Rosenborg in front of a crowd of just 24,973.
It was their third successive game without a win following a 2-0 defeat at Aston Villa and a goalless draw with Blackburn in the Premier League.
Those results have left Chelsea fifth in the table - two points behind leaders Arsenal and with a visit to Manchester United to come on Sunday.
The BBC understands the impasse between Mourinho and Abramovich came to a head after their 2-0 defeat to Aston Villa earlier this month.
Mourinho has been at loggerheads with the Russian since their disagreement over the lack of funds to sign players during last January's transfer window.
Mourinho's reluctance to play Ukraine international Andriy Shevchenko, brought in by Abramovich at a cost of £31m, and the Russian billionaire's desire to bring in Grant from Portsmouth to work with the misfiring striker only served to heighten the tension.
Abramovich wants his team to win trophies but also play with style
Grant was recruited in the summer as director of football and Mourinho is understood to have simmered ever since.
Former Chelsea player Pat Nevin says that behind the scenes movements were key to Mourinho's departure.
"He's a very individual man and he thinks he should be the power at the club," Nevin told 5live.
"If you put someone of that ego, and I say that in a likeable way, in charge and then you tell him you're not quite in charge, then I think it was a recipe for disaster."
Radio 5live football correspondent Legard agreed Mourinho's relationship with Abramovich would break down at some point.
"It suited both parties that he went," said Legard. "They've had an uneasy relationship, to put it mildly.
"One: the board, Roman Abramovich and the directors were frustrated by the results this season and also the style of play. They wanted stylish football. They wanted football which appealed to the world and they weren't getting it.
It's clear this relationship has been breaking up for a long time
BBC sport editor Mihir Bose on Mourinho and Abramovich
"Two: Jose Mourinho was frustrated by the interference. He could not do the job how he wanted."
BBC sport editor Mihir Bose added: "It's clear this relationship has been breaking up for a long time."
Former England manager Graham Taylor believes the beginning of the end came when Michael Ballack and Shevchenko were brought in, reportedly against Mourinho's wishes.
Taylor told 5Live: "Once you take away the authority the manager has in signing players, you're on a slippery slope.
"What I would say about Mourinho is his record is with underachieving players and when Shevchenko and Ballack came in, it disturbed the balance.
"They've never looked as fluid and that's because the manager probably did not himself believe that is the way they should be playing."
Mourinho still had three years left on his contract, worth about £5m a year, after agreeing a new deal in May 2005.
Please don't call me arrogant, but I'm European champion and I think I'm a special one
Mourinho introduces himself to the English press in 2004
At the time he signed that deal, he said: "My heart is with Chelsea and the fantastic group of players that I have but the vision of the owner and the board for the future of Chelsea is also one I want to be a part of.
"I cannot imagine another situation or another club where I could be happier. I am totally behind this project."
But the Chelsea board are thought to have become increasingly unhappy over the team's form at the beginning of the campaign.
Mourinho, who has reportedly been given a £10m pay-off by the Blues, will not be short of job offers.
Of the 185 games he was in charge of Chelsea, they won 124, drew 40 and lost 21, a record that includes a 60-match unbeaten run in Premier League matches at Stamford Bridge.
The statistics go some way towards justifying Mourinho's famous description of himself as "a special one", made during his first press conference as Chelsea boss.