Eoin Morgan said he had exceeded his own expectations after hitting a record-breaking 17 sixes in a one-day international inning during England's World Cup thrashing of Afghanistan.

Morgan's aerial assault helped the England captain to a career-best 148 as the hosts piled up 397 for six at Old Trafford on Tuesday.

Bottom of the table Afghanistan were never in the hunt, with pre-tournament favourites England winning by 150 runs to go top on net run-rate from champions Australia.

"Never have I ever thought I could play a knock like that. I'm delighted that I have," Morgan, who came in at 164-2, told reporters.

"Coming at a time when it was a 50-50 shout whether myself or Jos (Buttler) went in probably helped because after I'd faced a few balls I had no choice."

"I had to start taking risks because of him coming in next. After I got dropped (on 28) it was just a matter of keep going. One of those days."

Read | Eoin Morgan breaks record for most sixes in an innings

Asked about the feeling of hitting a six, Morgan said: "It's like hitting a golf ball off the tee." 

"If you think it's going straight, you're the only person that knows at the time. It's a very special feeling."

Morgan's feat saw him surpass the previous record of 16 sixes in an ODI inning shared by such renowned big-hitters Rohit Sharma, AB de Villiers and Chris Gayle.

"It's weird, very strange," said Morgan. "It's something, along with the innings, that I never thought I'd do."

- Leadership and belief -

The 32-year-old Morgan's leadership and his belief in aggressive cricket have been behind England's rise to the top of the ODI rankings after a woeful first-round exit at the 2015 World Cup.

But when it was suggested the left-hander had ignored his own advice by doubting his ability to play Tuesday's innings, Morgan replied: "To be fair, the last four years, I've probably played the best in my career, but that hasn't involved a 50 or 60-ball hundred. 

"I thought I could -- I would have it in the locker somewhere, but it's never happened. So I sort of gave up on it a little bit."

Morgan's 71-ball masterclass was all the more impressive as he had been doubtful for the match with a back spasm that prevented him from batting during England's win over the West Indies on Friday.

"Turning and stuff there was a little (issue), yeah. It took a bit of time before I could get confidence in moving," added Morgan, who said he had not had any injections on the morning of the game.

Tuesday's innings saw Morgan hit his 13th ODI hundred but 12th for England, after scoring one for his native Ireland.

Read | Eoin Morgan: The visionary who evoked aggression in the Three Lions

Morgan was once best known for unorthodox shots attributed to his childhood exposure to the Gaelic game of hurling.

But a significant feature of his Afghanistan demolition job was the number of textbook straight sixes he hit.

"I think I scored a lot squarer early on in my career whereas I look a little bit more down the ground now," he said.

Morgan made his England debut in 2009 after helping Ireland qualify for the 2011 World Cup.

After a brief 16-match Test career, a key factor reason behind his switch, he became one of England's pioneering limited overs specialists and a regular in the Indian Premier League.

Now he is looking to lead England to their first World Cup title, with Sri Lanka next up for his side at Headingley on Friday.

"If we can produce the level of intensity at which we operated today, it will leave us in a really good place," Morgan said.

Feature image courtesy: AFP / Dibyangshu Sarkar