Centurion Eoin Morgan admitted his record-breaking heroics against Afghanistan were beyond his "wildest dreams" after helping England move top of the Cricket World Cup standings.

The England captain smashed 17 sixes - the most by any batsman in an ODI - during a stunning 71-ball innings of 148 on the way to an emphatic 150-run triumph at Old Trafford on Tuesday.

It came after Morgan had been a doubt for the match after suffering a back spasm in the previous game against West Indies and his raft of maximums was the key contribution in what was also a new world record of 25 team sixes in an innings.

"I didn't think at any stage it was going to be my day," Morgan said. 

"Getting quite old, running around with a bad back, you never think you can produce an innings like this. I never thought in my wildest dreams I'd produce an innings like that.

"It was a special day. It was a tough game, Afghanistan are a side with a lot of potential and it's the World Cup. We're loving playing in it. On the big stage, it is nice to do.

"I think I have changed. Everybody probably plays the shots I probably started my career with now, so they're not as effective. I've come full circle and I'm probably stronger down the ground now than I've ever been.

"I haven't yet [put my back out]! Tomorrow's going to be a rough day, I think!"

The victory saw England, who have won four of their opening five matches, climb above Australia to top the table.

Jonny Bairstow (90) and the in-form Joe Root (88) also produced high-quality displays with the bat and Morgan could not be happier with the start his side have made to the tournament.

"Are we where we want to be? Yes," he added. "The next two or three games are pretty crucial for us. 

"We want to bring our level of intensity to every game we play. We don't want to slack off. Focusing on that and making that a priority is important to us.

"The intensity can still be there, but you will still make mistakes. 

"We managed to spill a couple of catches, which can happen. We'll try hard to improve the next few games. But as long as that's there, I think you can't fault the guys."

Afghanistan, meanwhile, are still searching for their first victory of the tournament, but captain Gulbadin Naib was philosophical in defeat after Morgan's masterclass.

"How they played was something special," he said. "Credit goes to Morgan, how he batted, I think it was one of the best innings I've seen from him."