A summer that involved the loss of two series and two captains would not normally be considered a successful one, but as Kevin Pietersen cradled his first piece of silverware as England captain on a bitter-cold, squally Cardiff evening, there was, even on such an inhospitable night, an unmistakable feeling of optimism.

Despite the losses to New Zealand in one-day cricket and to South Africa in Test cricket and the departures of Michael Vaughan and Paul Collingwood as Test and one-day captain respectively, the England who completed the summer were more settled and confident than the one who began it.

The personnel changed a little, with, crucially, Andrew Flintoff returning to the fold, but the biggest difference was Pietersen - the catalyst for all the good things that happened since confusion threatened to wash over the England set-up once Vaughan had decided that enough was enough. Pietersen could barely have made a more impressive start to combining both roles; indeed, it is difficult to think of an England captain who has.

We were not to know it at the time, but when Vaughan returned from New Zealand to contemplate another summer in charge of the national team, he was having the first of the self-doubts that engulfed him before the series against South Africa was done. Collingwood's admission that he found the extra pressures too much after only 12 months in the one-day job meant that England began the summer with one captain who was near the end of his tether and one who was ill-suited to its peculiar demands.

It is no shame to admit, as Collingwood did, that you are not suited to the top job - few are - but it was clear from the moment Pietersen stepped out in the fourth Test against South Africa at the Brit Oval last month that here was a natural-born leader. It is ridiculous to pass judgment after such a short time, but some cricketers seem to grow with the extra responsibility and some are diminished. Pietersen lifted the England captaincy as if off the peg and at the moment the fit is just so.

Initial impressions are important and Pietersen's first move was of a man who knew his mind and who wanted to captain in a manner true to his attacking instincts. Accordingly, Flintoff was restored to the No6 berth, which enabled England to play five bowlers and sent a message to Flintoff that having a merry slog at No7 was not good enough. Flintoff responded to this encouragement, and the further confidence the captain showed when he pushed him up to No5 in the one-day team, so that by the end of the summer he resembled a proper batsman again, stroking rather than clubbing, batting rather than slogging.

Stephen Harmison has felt the full force of Pietersen's love and has responded if not in kind then certainly with his most consistent showing for two years. It was immediately noticeable how, when discussing Harmison, the captain personalised everything: Harmison was his pick, is his champion and is bowling for him. As ever with Harmison, desire is the key and Pietersen's love-fest has made him feel wanted and valued and has rekindled the bowler's ambition.

This Pietersen-Flintoff-Harmison effect was too much for a South Africa team who had taken their eyes off the ball. How far the 4-0 triumph in the NatWest one-day series was England playing above themselves or South Africa struggling is a moot point, but on this form England will challenge any team at home. The next trick for the arch conjurer Pietersen is for England to start competing away from home in conditions that will demand more inventiveness and guile with the ball.

But at least by the end of the summer the balance of the team had been transformed and those tricky middle overs that often meander by with England about as threatening as a poodle became favoured territory. At a time when batsmen were looking to throw off the shackles of the new-ball threat, Flintoff took ten wickets and Harmison five. South Africa never got away.

So the manner of England's one-day triumph has been no fluke. The captain has demanded more from his men; the senior players led the way and the rest responded. Those returning did so with such conviction that previous omissions seemed puzzling. Matt Prior, for instance, responded to the freedom on offer at the top of the order, his natural attacking instincts were given full licence and even the catches behind the stumps began to stick once the fug of doubt and uncertainty had been removed.

Newcomers such as Samit Patel played like old hands and, for the first time in an age, England's one-day team added up to more than the sum of the parts: long in batting, full of options with the ball and athletic in the field. I have been bearish about England's one-day team for longer than I can remember, but I am buying their stock right now. If Pietersen can keep them focused and driven, winning a leading one-day tournament is within their capabilities.

Success and confidence feed off each other and England can take this late-season surge into the winter and beyond. There are a few hurdles to overcome. How will Pietersen respond if things go pear-shaped? Will what seemed at first glance a fragile partnership between the new captain and head coach weather the storms that will come their way? How can, and should, Vaughan return if the runs start to flow again?

For now, Pietersen can take a breather and reflect on a magnificent start to the latest phase of his career. Then there is some plotting and planning to be done, for the start of the Ashes is nine months hence and, as ever, reputations will be made or broken according to their destiny.