How many times in one summer should a captain be expected to save his job? In the eyes of England's selectors, probably only once. Alastair Cook re-established his authority as England's Test captain during their 3-1 defeat of India in the Investec Test series. His resilience could not have been clearer. It would be immensely wearying for him to imagine that he might have to do it all again.

In these days of split captaincy, securing a position as Test captain, however redoubtable the effort, is not automatically useful now England face seven months of unbroken ODI cricket, climaxed by the 2015 World Cup in Australia and New Zealand.

Cook's Test career has always been his strongest suit. His place in the one-day side has been debated regularly. The debate will continue, even if only at a low level, but all the signs are that it is an irrelevant one.

He might have built a castle in the mountains only to find the next campaign is on the coast. But he has benefited from the examination of his captaincy credentials. His leadership is no longer an inheritance, it is now a thing of substance.

That England's selectors are intent on Cook leading England in the World Cup is apparent. Barring disasters, any debate is superfluous. The chance to make a change was now, ahead of a Royal London ODI series against India - the first of them in Bristol on Monday - more 50-over cricket in Sri Lanka before Christmas and a triangular series in Australia, with India the third participants, in the New Year.

But they had little heart for it, especially when one of the strongest candidates, Eoin Morgan, was having such a dismal time in charge of Middlesex. Instead they are calculating that signs of a new England Test side coming together will feed positively into the 50-over side.

The decision taken, the time has come for consistent planning. England can now commit time to addressing their long-perceived cricketing weaknesses in the 50-over format. No longer will they have to do this as an afterthought. It is what this run of one-day series was designed for.

"We haven't had this period ever - certainly not since I started - where you have had just one-day cricket for seven months," Cook said. "There's time to dedicate to practicing those skills that are needed for one-day cricket, especially the extra skills you need like in the Powerplay overs, both with bat and ball, and death bowling. And that is what we will need to do if we are to have a chance of winning the World Cup in what will be good conditions for us."

Changes are subtle ones. Cook will have a new opening partner in Alex Hales, who he suggested would be given the entire series to prove himself. Ian Bell is also scheduled to bat at No. 3. Hales gives England more energy at the top of the order, but it is his ability to make hundreds - four of them in 50-over cricket in the wink of an eye - which has finally persuaded England's selectors to turn to him.

"He is a different batter to the other guys - he hits the ball incredibly hard, in different areas, with an unorthodox technique" Alastair Cook on Alex Hales

Cook will benefit from the change, but he knows he cannot regard Hales' presence as permission to potter on at whatever rate he chooses. A captain with a career strike rate in ODIs of 78 runs per 100 balls has been paired with a young buck with a List A strike rate of 100. But Cook is keen to point out that since his return to England's ODI side, his strike rate is above 80 runs per 100 balls. He knows that cannot be allowed to diminish.

"I don't think it changes my role," he said, of Hales' inclusion. "The job of the top four or five is to try and score a hundred and win the game, by setting up the game. You have to try and do it in your way. What's pleasing about Alex over the last month or so is that he has scored four centuries for Nottinghamshire and at a good rate too.

"He is a different batter to the other guys - he hits the ball incredibly hard, in different areas, with an unorthodox technique. He's done really well in T20 cricket and he's got the opportunity over these five games to show us what he can do in 50-over cricket."

Suggestions of a major overhaul of the ODI squad were wide of the mark. The only obvious victim is Ravi Bopara and because of his all-round ability with bat and ball, his absence causes England immediate selection problems.

The exclusion of Bopara essentially commits England to a five-bowler strategy for the World Cup, believing that a phalanx of high-quality seamers is their strongest chance of belying their outsiders status in Australia and New Zealand with a strong challenge.

Hales' inclusion must therefore impact on a batsman. As unlikely as it seems, with Bell earmarked for No. 3, Gary Ballance or Joe Root could be in contention for the No. 4 spot, followed by Eoin Morgan, either Moeen Ali or Ben Stokes as an allrounder, and the wicketkeeper Jos Buttler.

Bristol has had a welcome makeover, so becoming the latest England ground to make definite advances in the past decade or so, but for all that it remains England's most rudimentary international venue. It does not immediately strike you as a place where successful World Cup campaigns are first bedded in, and England do not strike many as potential World Cup winners. It is time for them to try to change that perception.