Matt Prior has been rewarded for his fine Ashes series with a surprise World Cup-2011 berth

England's squad for the one-day series against Australia was named in mid-December and a month has proved a long time in cricket. Prior timed his Ashes form well, finishing the series with 85 in Melbourne and 118 in Sydney, then joined Victoria for the Big Bash which meant he was never far from Flower's view.

"The circumstances have changed," Andy Flower, the England team director, said. "Matt Prior did very well out here for the Test matches. He is a combative aggressive cricketer and he fits our aggressive fielding unit. So those are the reasons why he's been picked for the World Cup.

"It was a tough decision," Flower added. "We always knew the timing of the World Cup announcement would be tricky. It's not ideal one game into a seven-match series. Steve Davies was picked in our last one-day series in England and he did OK against Pakistan.

"We picked him for this series in Australia because of the conditions out here. But as we get closer to the World Cup we've made that adjustment and we want Prior to get a few games under his belt before we get out there so he's going to be arriving in Hobart [on Wednesday]."

Another aspect in Prior's favour will have been his near-faultless work with the gloves during the Ashes series and he is now a world-class keeper. Davies is solid, but the subcontinent can be a tough place for wicketkeeper's and in one-day cricket, where the smallest margins matter, it could prove valuable to have Prior's class behind the stumps.

This isn't the first time Flower has been involved in significant selection calls around a global tournament. At the World Twenty20 in the Caribbean, James Anderson missed out for the entire campaign when it was decided Ryan Sidebottom's left-arm angle and control of yorkers was a better option. Flower has a ruthless streak and Davies has just found that out.

"Of course he's disappointed, any player would be disappointed to be left out of the England side," Flower said. "It means a lot to our players. They're very difficult decisions to make because they affect people's careers, but those are the harsh realities of playing professional sport and Steve and others that are left out will have to accept it."

The other marginally contentious positions in the final 15-man squad were the back-up bowlers, but it was widely expected that Ajmal Shahzad, preferred ahead of Chris Tremlett or Chris Woakes, and James Tredwell, the Kent offspinner, would get the nod.

With England's plans revolving heavily around two spinners they need a frontline option in reserve should illness or injury strike, and Graeme Swann will also miss the warm-up period to be at the birth of his first child, while Shahzad has impressed in his brief international appearances so far.

"We wanted to make sure we not only had two frontline spinners or a third in case of injury or illness out there," Flower said. "Spin will play a significant part in the World Cup, there's no doubt. Shazhad was very impressive in the last game that we played in Melbourne. He's been in and around our squad for a while now, just getting tastes of international cricket and hasn't secured a spot yet. We think he shows a lot of potential. He can reverse swing the ball which will be important on the subcontinent and he's a good competitor."

At the other end of the experience scale is Paul Collingwood, England's most capped one-day cricketer, who was dropped for the first match against Australia following his poor Ashes and Twenty20 form. Andrew Strauss said Collingwood needed time away from the spotlight and Flower believes the allrounder, who is also on paternity leave in the build-up to the World Cup, still has a crucial role to play.

"He missed out the last game but his experience, his credentials as a player, the energy he gives in the field and the quality of his fielding and obviously the all-round capabilities with bat and ball make him a strong contender," he said. "The reason why he was left out in the first place was he was struggling recently and needs a little time to reassess but he'll be back in the side."

Now that the final 15 has been named preparations can swing into full gear for the tournament which starts on February 19. England's first match is against Netherlands, in Nagpur, three days later and Flower said there will be a duel focus to the rest of the one-day series in Australia.

"It's a balance of both," he said. "This series is important in its own right. It is very important series for our preparation for the World Cup. Some of our training will evolve around subcontinent-type methods and certainly we'll be working towards that. I think our one-day cricket has improved significantly over the last couple of years and I believe that we can do well."