Scorecard | Action in images
London: Eoin Morgan's rapid 89 not out laid the platform for England's 15-run win over arch-rivals Australia in the first one-day international at Lord's here on Friday.
Victory kept alive England's hopes of replacing their oldest foes as the world's top-ranked one-day side and topping the standings in all three formats, although they need to sweep this campaign 5-0 to knock Australia off their 50-over perch.
England were struggling when left-hander Morgan, on his Middlesex home ground, came in at 121 for three.
But the former Ireland international, the man-of-the-match, broke the shackles with a 63-ball innings featuring four sixes and five fours to propel England to 272 for five.
He shared stands of 68 with Jonathan Trott (54) and 83 with Craig Kieswetter, out for 25 off the last ball the innings after Australia had won the toss.
Australia, chasing 273 for victory, saw captain Michael Clarke top-score with 61 after opener David Warner had made 56.
But England's bowlers were largely on top, with all their four seamers taking two wickets apiece.
Australia opener Shane Watson fell for just 12 when he was caught behind off Middlesex fast bowler Steven Finn, although England had to review Pakistani umpire Aleem Dar's original not out decision before the all-rounder exited.
But left-hander Warner and George Bailey settled into a partnership of 76.
However, that second-wicket stand ended when Bailey played on to senior paceman James Anderson.
Warner's impressive 61-ball innings, including a six and five fours, came to a close when he edged Anderson and wicket-keeper Kieswetter, diving to his left, held the first of four catches in the innings.
At that stage, both Clarke and David Hussey were on nought.
The run-rate slowed and Hussey made just 13 before a Finn bouncer hit his helmet and deflected onto the stumps to leave Australia 132 for four.
Clarke and wicket-keeper Matthew Wade got Australia back into the game with a stand of 57 at better than a run-a-ball.
Wade pulled Anderson for six and Clarke drove off-spinner Graeme Swann high over the top to seal a 59-ball fifty.
However, a dreadful mix-up ended with Wade run out as he sacrificed his wicket on behalf of his skipper.
Tim Bresnan then captured the prize wicket of Clarke after the batsman swung across a low full toss and was plumb lbw.
After Stuart Broad had taken two wickets for five runs in six balls, Australia were 231 for nine.
But Brett Lee and last man Xavier Doherty held on to leave Australia with a target of 21 off the last over, from Finn.
However, Finn kept his nerve and conceded just five runs as England beat Australia in a one-day international at Lord's for the first time since 1997.
Earlier Ian Bell, who in his two previous innings during a 2-0 series win over the West Indies had made a hundred and a fifty, was the first England wicket to fall when lbw to Lee for 41.
Soon afterwards teenage fast bowler Pat Cummins took his first wicket against England when he had home captain Alastair Cook caught behind for 40.
Trott, missed on 38 when Cummins dropped a caught and bowled chance, completed a 65-ball fifty with just three fours before effectively yorking himself when bowled by left-arm spinner Doherty.
However, Morgan struck successive Lee deliveries for six over long-on and made it three in as many balls faced with a pull off Watson.
The series continues across London at The Oval on Sunday.