Hales smashed six sixes and 11 fours in an unbeaten 116 as England made their biggest successful chase in the shortest format.
After a controversial decision reprieved Mahela Jayawardene (89) first ball, Michael Lumb having appeared to take a low catch, and some lamentable fielding, including three simple drops, allowed Sri Lanka to post a testing 189 for four and England were in deep trouble at nought for two after the first over.
Eoin Morgan (57) and Hales put on 152 for the third wicket to completely turn the match around before Morgan and Jos Buttler (two) departed in quick succession. Big-hitting Hales and Ravi Bopara saw England home with four balls to spare.
“I’m absolutely buzzing with that,” Hales said. “Centuries in this format don’t come along very often and I’ve got out a couple of times in the 90s so I was pleased to get over the line today. It’s a great win for us. We weren’t in good form coming into this match but we needed that and I’m buzzing for it.”
England lost their first game of the World Twenty20 to New Zealand in controversial fashion via the Duckworth-Lewis method and Hales is now keen to look forward.
“We felt a little bit hard done by the other night,” he said. “We posted a fairly good score and felt we could have defended it. But it’s great to get a win on the board and hopefully there’s a couple more to follow.”
Captain Stuart Broad was quick to heap praise on Hales, labelling his innings, which included six sixes and 11 fours, as one of the best he had seen by an England player.
“That’s a very special knock, one of the best I’ve seen in an England shirt,” he said. “To take the responsibility and have the run-rate that we had, to keep up with that all the way through, and then to win it with a few balls to spare is very special.”
Much has been said about the dew in Bangladesh making conditions difficult for fielding sides but Broad was reluctant to use that as an excuse and insisted his team just have to get on with it.
“We really messed up on that, dropping five or six catches, and really key men,” he said.
“We’ve got away with it today with an unbelievable knock from two of our guys but we’ll have to raise our standards with the catching a little bit come the next game.
“It’s extremely wet out there, the seam is virtually impossible to dry. It just makes you as a bowler a little bit unsure when you’re going for the yorker.
“We’ve been fielding with wet balls in practice but we’ll have to make them wet balls of soap I think.”
England now face games against South Africa and Holland as they bid to make the semi-finals and Broad is hopeful that they can take some confidence from yesterday’s performance.
He added: “We know in these World Cups, they’re always about momentum at the right time and that sort of knock from Hales, but also by Morgs, will give our changing room a huge amount of belief.”
“We’ve got to win both those games and I believe we can do that. The confidence we will get with the bat from the two games that we’ve played, getting 170 against New Zealand and then chasing this down today is massive.”
Sri Lanka captain Dinesh Chandimal admitted that the conditions made it difficult for his spinners but was quick to praise England’s batsmen. He said: “Alex played really well, he played exceptionally well. There is a lot of dew. Bowlers can’t grip the ball and especially we didn’t bowl really well. We had two spinners, they can’t grip the ball, especially [Ajantha] Mendis.”
Earlier, South Africa narrowly averted embarrassment as they edged past Holland by six runs. The Dutch, routed for a record low 39 all out against Sri Lanka on Monday, came out with a point to prove with Ahsan Malik taking five for 19 to restrict the Proteas to 145 for nine.
A brutal half-century from Pretoria-born opener Stephan Myburgh took Holland to 114 for four in the 12th over. That left them needing only 32 from 48 balls but Imran Tahir took two wickets in an over to shift the momentum. Holland kept losing wickets to rash shots and lost their final wicket to Beuran Hendricks with just seven runs needed.