Australia ended their tour of England on a high with a 3-2 victory in the one-day international series as home captain Eoin Morgan suffered concussion after being hit on the head by a bouncer.
Mitchell Marsh had earlier picked up four for 27 as England were dismissed for just 138 in 33 overs with Ben Stokes (42) and Adil Rashid (35 not out) the only players to really trouble the Australia attack.
England played the majority of the match without skipper Morgan, though, after he was struck on the helmet by a short ball clocked at 90mph from Mitchell Starc in the seventh over the game.
Morgan, who scored one run and faced six balls prior to the blow, was hit just below his right ear as he turned his head away.
With the death of Australia opener Philip Hughes to a short ball in a first-class match in Sydney last November still fresh in the mind concerned Australian players quickly surrounded the Dublin-born left-hander.
Following treatment by the England medical staff on the pitch the 29-year-old climbed to his feet and groggily made his way back to the dressing room, but was deemed unable to continue with James Taylor charged with skippering the hosts for the remainder of the contest.
It proved an impossible task for Taylor with so few runs on the board as Australia made light work of England’s total.
England’s spirits were raised briefly when Australia opener Joe Burns departed for a duck after he swished wildly at a delivery from David Willey and a feathered edge found the gloves of England wicketkeeper Jonny Bairstow.
England also secured the prize wicket of Australia captain Steve Smith when he nicked an attempted drive to Bairstow off Mark Wood as second wicket went down with the score on 31.
However, Finch’s assault on the England bowlers proved to be the difference as he showed some clean hitting to reach his half-century off 47 balls, taking a particular fancy to Rashid’s leg-spin.
Finch shared an unbroken stand of 109 with George Bailey, who hit the winning runs to finish unbeaten on 41.
Earlier, England had entered the decisive match brimming with confidence after they fought back to square the series at 2-2 with a three-wicket win at Headingley on Friday.
And, having won the toss and then watched his side compile 300-8 then bowl Australia out for 207 at the same venue in the third ODI last week, skipper Morgan again elected to bat when he called correctly.
However, Australia’s pace attack bowled tight lines and aggressively with man-of-the match Marsh the pick as they took wickets at crucial times to bowl England out in 33 overs.
England lost Jason Roy (4) lbw to Starc early on, although replays showed the ball had been missing the stumps but the opener took too long to decide whether to review the decision.
Alex Hales (4) and Taylor (4) were both removed by John Hastings, who claimed three for 21, before Morgan left the field.
Stokes added a degree of respectability to the score with a 51-ball 42 which included six fours and one six while Rashid boosted the total in a last-wicket stand of 32 with England debutant Reece Topley.
However, their partnership was brought to a halt when the stoic Topley was trapped plumb lbw by spinner Ashton Agar for six to leave Australia with a comfortable chase.