"They are not at the must-win stage yet but, with difficult matches against hosts India, Pakistan, Australia and South Africa to come, England's backs are well and truly up against the wall," is the verdict of my colleague Matthew Henry from Delhi.
Scroll down for a brief recap of what happened on a monumental day for Afghanistan including all the post-match reaction including England captain Jos Buttler, and Afghanistan coach Jonathan Trott.
The Test Match Special team are busy recording a podcast which will pick the bones out of this defeat and analyse where England go from here.
The tournament continues on Monday as winless Australia face Sri Lanka in Lucknow and we will have live text commentary of that on the BBC Sport website, and ball-by-ball coverage on Test Match Special from 09:15 BST.
England will have a much closer eye on the result of games elsewhere now you would imagine.
Match recap...
England were really in the mire at 91-4 when England captain Jos Buttler fell for a scratchy nine off 18 balls.
Hopes were pinned on Harry Brook, who made England's only half-century, but when he was bowled by spinner Mujeeb Ur Rahman for 66 the game was effectively up.
Rashid Khan took the final wicket, bowling Mark Wood, as England were knocked over for 215 and Afghanistan celebrated.
Post update
England lost Jonny Bairstow early in their response to a contentious DRS decision but their innings never really got going as the key wickets of Dawid Malan and Joe Root also went down.
Post update
A quick recap then. The tone for England's day began with the first ball of the day when Jos Buttler allowed a wide ball from Chris Woakes to slip through his legs.
Opener Rahmanullah Gurbaz provided the backbone of Afghanistan's total of 284 - taking a particular shine to Chris Woakes, who bowled four wicketless overs for 41.
Leg-spinner Adil Rashid (3-42) hauled England back into the contest as Afghanistan went from 114-0 to 174-5 before some late-order resistance boosted their total.
'If we can just get it together, we can take on anyone'
More from Afghanistan coach Jonathan Trott on TMS: "My first ODI series, we probably should've beaten Sri Lanka. We've beaten Pakistan in a T20 series, we've beaten Bangladesh away as well. They're capable of so much.
"Hopefully, a win like this can give them the confidence to get over the line. The self-belief to win on the big stage and beat the big teams - and put a smile on everyone's face.
"With the bat we need to put together a good 50 overs which we haven't in three games so far. We're a work in progress.
"I'm not going to look too far ahead. We've got a game in three days time.
"We've won one game out of three, let's not jump too far ahead.
"Every game that I'm coach of this side I want to win and they can win, especially in these conditions. England are still a good side and I'm sure they'll be there or thereabouts after nine games.
"Tonight we played really well and we didn't allow them to play their natural game. A few tings went our way but you need that in these games when you're the underdogs.
"This just confirms the talent I see in the side and if we can just get it together, we can take on anyone."
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John: Can we please now start talking about the fact that Buttler is a poor white ball captain?T20 WC was a fluke rescued by some epic performances with the bat. Tactically and motivationally he’s not a patch on Morgan.
Post update
Daniel Norcross
BBC Test Match Special commentator
Dare you say, England's defence of the World Cup is in peril.
Post update
Henry Moeran
BBC Test Match Special commentator
This is the sort of result that can really derail a side in a tournament.
Post update
Alex Hartley
Former England bowler on BBC Test Match Special
Sometimes when you're under the pump and every game is a knockout game, you can play better.
England have been quite tentative. They talk about running into the fire and taking the game on but we haven't seen them do that.
Post update
Devender Kumar
BBC Test Match Special commentator
I wasn't surprised because I have seen the talent in the batting line-up and everyone knows about the potency in the bowling with Mujeeb Ur Rahman, Rashid Khan and Mohammad Nabi bring.
On a surface where there was something for the spinners, they would be expected to deliver and they did. The dew didn't set in and that helped Afghanistan in checking the English batters.
'I'm a little bit in shock'
Getty ImagesCopyright: Getty Images
Afghanistan coach Jonathan Trott, speaking to BBC Test Match Special: "It's a huge occasion. A second World Cup win in the 50-over competition.
"But also, after the two defeats we had, to bounce back like that shows the character we have in the dressing room.
"By no means a perfect performance, there is a lot we can work on but, jeez, we got a lot right as well. I'm buzzing, very excited and I'm going to enjoy tonight.
"Then I'll start focusing on Chennai and the next match there.
"It's recognition of the hard work we've but in but also what we can achieve as a side when we get things right.
"We had a really good start then fell away a bit with the bat. Yes, the pitch was spinning.
"I'll take stock at the end, I'm a little bit in shock at the moment. It's a great feeling, I just hope we have more of these in this campaign."
Post update
Afghanistan coach Jonathan Trott has just spoken to the media and we'll have his thoughts with you very shortly.
Post update
Daniel Norcross
BBC Test Match Special commentator
Not for the first time in India, Jonathan Trott may be seen as the reason for England's travails at a World Cup.
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SMS Message: England feel disjointed because they are. The team has been chopped and changed, players unretiring and others out of form playing. It's a mess, with no core, no obvious direction, no cohesion. from Tim
England feel disjointed because they are. The team has been chopped and changed, players unretiring and others out of form playing. It's a mess, with no core, no obvious direction, no cohesion.
Post update
Steven Finn
Former England bowler on BBC Test Match Special
Afghanistan have put a lot of other teams on notice today.
They're very dangerous, they've got a lot of good players and if they piece it together then they're going to win a number of games through this tournament and upset people along the way.
Post update
Here's how the World Cup table looks as things stand...
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SMS Message: Dilemma for next game. Who do you drop to bring Stokes in. Open with Stokes and drop Bairstow or drop Buttler and Bairstow as keeper. We can't drop Brook. from Keith, Yorkshire
Dilemma for next game. Who do you drop to bring Stokes in. Open with Stokes and drop Bairstow or drop Buttler and Bairstow as keeper. We can't drop Brook.
Drop Jos Buttler? The captain of the side and arguably England's greatest white-ball player? Keith, come on.
Post update
Daniel Norcross
BBC Test Match Special commentator
Ben Stokes should be back soon and England will need him and his talismanic qualities.
Post update
Steven Finn
Former England bowler on BBC Test Match Special
The only England resistance came from Harry Brook and there was some meek and timid dismissals.
Jos Buttler and the England management team do not look like happy people right now.
Post update
Our man in Delhi, Matt Henry, has filed his match report from the Arun Jaitley Stadium.
"They are not at the must-win stage yet but, with difficult matches against hosts India, Pakistan, Australia and South Africa to come, England's backs are well and truly up against the wall," he writes.
"This defeat was similar to their opening-day loss to New Zealand. They were poor with the ball and, Harry Brook aside, hardly laid a glove on their opponents with the bat."
Live Reporting
Timothy Abraham, Sam Drury and Jonty Colman
All times stated are UK
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BBC SportCopyright: BBC Sport 
Latest PostJoin us on Monday...
"They are not at the must-win stage yet but, with difficult matches against hosts India, Pakistan, Australia and South Africa to come, England's backs are well and truly up against the wall," is the verdict of my colleague Matthew Henry from Delhi.
You can read the unabridged version of his match report here...
Scroll down for a brief recap of what happened on a monumental day for Afghanistan including all the post-match reaction including England captain Jos Buttler, and Afghanistan coach Jonathan Trott.
The Test Match Special team are busy recording a podcast which will pick the bones out of this defeat and analyse where England go from here.
That will be available to listen online or download here in a short while...
The tournament continues on Monday as winless Australia face Sri Lanka in Lucknow and we will have live text commentary of that on the BBC Sport website, and ball-by-ball coverage on Test Match Special from 09:15 BST.
England will have a much closer eye on the result of games elsewhere now you would imagine.
Match recap...
England were really in the mire at 91-4 when England captain Jos Buttler fell for a scratchy nine off 18 balls.
Hopes were pinned on Harry Brook, who made England's only half-century, but when he was bowled by spinner Mujeeb Ur Rahman for 66 the game was effectively up.
Rashid Khan took the final wicket, bowling Mark Wood, as England were knocked over for 215 and Afghanistan celebrated.
Post update
England lost Jonny Bairstow early in their response to a contentious DRS decision but their innings never really got going as the key wickets of Dawid Malan and Joe Root also went down.
Post update
A quick recap then. The tone for England's day began with the first ball of the day when Jos Buttler allowed a wide ball from Chris Woakes to slip through his legs.
Opener Rahmanullah Gurbaz provided the backbone of Afghanistan's total of 284 - taking a particular shine to Chris Woakes, who bowled four wicketless overs for 41.
Leg-spinner Adil Rashid (3-42) hauled England back into the contest as Afghanistan went from 114-0 to 174-5 before some late-order resistance boosted their total.
'If we can just get it together, we can take on anyone'
More from Afghanistan coach Jonathan Trott on TMS: "My first ODI series, we probably should've beaten Sri Lanka. We've beaten Pakistan in a T20 series, we've beaten Bangladesh away as well. They're capable of so much.
"Hopefully, a win like this can give them the confidence to get over the line. The self-belief to win on the big stage and beat the big teams - and put a smile on everyone's face.
"With the bat we need to put together a good 50 overs which we haven't in three games so far. We're a work in progress.
"I'm not going to look too far ahead. We've got a game in three days time.
"We've won one game out of three, let's not jump too far ahead.
"Every game that I'm coach of this side I want to win and they can win, especially in these conditions. England are still a good side and I'm sure they'll be there or thereabouts after nine games.
"Tonight we played really well and we didn't allow them to play their natural game. A few tings went our way but you need that in these games when you're the underdogs.
"This just confirms the talent I see in the side and if we can just get it together, we can take on anyone."
Get Involved
#bbccricket
John: Can we please now start talking about the fact that Buttler is a poor white ball captain?T20 WC was a fluke rescued by some epic performances with the bat. Tactically and motivationally he’s not a patch on Morgan.
Post update
Daniel Norcross
BBC Test Match Special commentator
Dare you say, England's defence of the World Cup is in peril.
Post update
Henry Moeran
BBC Test Match Special commentator
This is the sort of result that can really derail a side in a tournament.
Post update
Alex Hartley
Former England bowler on BBC Test Match Special
Sometimes when you're under the pump and every game is a knockout game, you can play better.
England have been quite tentative. They talk about running into the fire and taking the game on but we haven't seen them do that.
Post update
Devender Kumar
BBC Test Match Special commentator
I wasn't surprised because I have seen the talent in the batting line-up and everyone knows about the potency in the bowling with Mujeeb Ur Rahman, Rashid Khan and Mohammad Nabi bring.
On a surface where there was something for the spinners, they would be expected to deliver and they did. The dew didn't set in and that helped Afghanistan in checking the English batters.
'I'm a little bit in shock'
Afghanistan coach Jonathan Trott, speaking to BBC Test Match Special: "It's a huge occasion. A second World Cup win in the 50-over competition.
"But also, after the two defeats we had, to bounce back like that shows the character we have in the dressing room.
"By no means a perfect performance, there is a lot we can work on but, jeez, we got a lot right as well. I'm buzzing, very excited and I'm going to enjoy tonight.
"Then I'll start focusing on Chennai and the next match there.
"It's recognition of the hard work we've but in but also what we can achieve as a side when we get things right.
"We had a really good start then fell away a bit with the bat. Yes, the pitch was spinning.
"I'll take stock at the end, I'm a little bit in shock at the moment. It's a great feeling, I just hope we have more of these in this campaign."
Post update
Afghanistan coach Jonathan Trott has just spoken to the media and we'll have his thoughts with you very shortly.
Post update
Daniel Norcross
BBC Test Match Special commentator
Not for the first time in India, Jonathan Trott may be seen as the reason for England's travails at a World Cup.
Get Involved
Via WhatsApp on 03301231826
Post update
Steven Finn
Former England bowler on BBC Test Match Special
Afghanistan have put a lot of other teams on notice today.
They're very dangerous, they've got a lot of good players and if they piece it together then they're going to win a number of games through this tournament and upset people along the way.
Post update
Here's how the World Cup table looks as things stand...
Get Involved
Text 81111 (UK only - standard message rates apply)
Drop Jos Buttler? The captain of the side and arguably England's greatest white-ball player? Keith, come on.
Post update
Daniel Norcross
BBC Test Match Special commentator
Ben Stokes should be back soon and England will need him and his talismanic qualities.
Post update
Steven Finn
Former England bowler on BBC Test Match Special
The only England resistance came from Harry Brook and there was some meek and timid dismissals.
Jos Buttler and the England management team do not look like happy people right now.
Post update
Our man in Delhi, Matt Henry, has filed his match report from the Arun Jaitley Stadium.
"They are not at the must-win stage yet but, with difficult matches against hosts India, Pakistan, Australia and South Africa to come, England's backs are well and truly up against the wall," he writes.
"This defeat was similar to their opening-day loss to New Zealand. They were poor with the ball and, Harry Brook aside, hardly laid a glove on their opponents with the bat."
You can read the full report here...