Centurion Eoin Morgan paraded his limited-overs prowess to carry England to a four-wicket win and a 1-0 NatWest Series lead over Australia at the Rose Bowl.
Morgan (103no) and Luke Wright joined forces at 97 for four in pursuit of 267 for seven but, like Australia's Michael Clarke (87no) before them, refused to panic under pressure.
Clarke had shared half-century stands with Mike Hussey and James Hopes to ensure a testing target under lights. After the hosts then stumbled from 75 for one, their challenge had a still more significant look to it.
But a 95-run partnership in 15 overs kept them in with a near even chance - and after losing Wright, Morgan's uncanny ability to pace an innings and pick and execute the right shots helped England home with a misleading four overs to spare.
The Irishman's deft deflections and powerful drives brought him 16 fours from only 85 balls in his third one-day international hundred, and prevented his adopted country losing a ninth match in their last 10 attempts in this format against Australia.
He still needed support from the lower order, though - and it duly came from Tim Bresnan, whose survival on 10 by a hair's breadth third-umpire run-out decision early in a match-clinching stand of 71 was an apt indicator of a closely-fought series opener.
Bresnan was yorked by Ryan Harris (three for 42) with victory in sight, allowing Morgan to finish the contest with a boundary off the same bowler.
After Clarke's highest ODI score against England had helped Australia post a challenging target, the home chase got off to a frenetic start.
Andrew Strauss picked up two fours off his legs in Doug Bollinger's first over, only to then edge Harris behind when he tried to drive down the ground.
Kevin Pietersen joined Craig Kieswetter, and Harris was convinced he had his man for nought - again caught behind, driving - but the number three, and umpire Ian Gould, saw things differently.
Pietersen was soon seeking to dominate on the front foot in a stand of 59 but was cut off in his prime when he went after one ball too many and speared a catch low to Ricky Ponting at point, off Shane Watson.
Kieswetter was bowled attacking teenage debutant Josh Hazlewood on the back foot, and Paul Collingwood mistimed an attempted big hit at Watson into the hands of mid-off.
But Wright played a fine hand, until he was lbw aiming across the line at Harris, helping Morgan to jockey a position from which he could close out the match. Clarke, who hit seven fours from 97 balls, had needed patience and good sense at what was once his home venue to eke out a near par total after Australia lost four top-order wickets for only 46 runs.
He put on 70 with Hussey and then 57 with Hopes for the fifth and sixth wickets - gradually increasing the tempo until 78 came off the final 10 overs.
The suspicion was that Australia were losing their way after winning the toss, on a pitch of decent pace and true bounce in glorious conditions.
But Clarke measured the recovery, taking 30 balls before collecting his first boundary - a cut off Graeme Swann - and although fours, let alone sixes, remained hard to come by, the end product was vindication of the Australia vice-captain's methods.
Openers Watson and Tim Paine had begun the innings cautiously - only two coming from James Anderson's first over and Bresnan beginning with a maiden - but still posted a half-century stand at a run-a-ball.
Watson escaped a half-chance on three when he bludgeoned Anderson through the diving hands of Wright at midwicket, and he also had a couple of minor lbw scares.
But England were in increasing need of a breakthrough when Stuart Broad struck with his fifth delivery.
Watson had already hit two leg-side fours off him and was aiming for another but could only lob a tame catch back at the bowler as an attempted pull hit the splice.
Enter Ponting, doubtless entertaining high hopes of marking the world's 3,000th ODI with a major personal contribution.
But first another Strauss bowling change bore immediate fruit, Wright successful with only his second ball as Paine chopped a length delivery on to his stumps.
Then Ponting himself also fell to Wright, getting underneath a pull and holing out at long-leg.
After Cameron White had inside-edged Anderson on to his stumps, Australia were wobbling.
But they had the right men for a mini-crisis in Clarke and Hussey, who chipped low-risk runs into gaps for the next 13 overs until the left-hander edged a cut behind off Mike Yardy immediately after the mandatory ball change.
Clarke was far from done with, though, and gave Hopes licence to attack - before linking up with Nathan Hauritz too, to such effect that England were to need all of Morgan's ingenuity to edge the verdict.