Watson smashed 143 as Australia amassed 298. England were bowled out for 249, 50 runs short of the target.
Southampton: Shane Watson's century saw Australia to a 49-run win over England in the fifth one-day international at Southampton on Monday as their lengthy tour ended with a 2-1 series victory. (Scorecard | Commentary)
Story first published on: Monday, 16 September 2013 18:41
Watson, involved throughout in a trip that saw Australia arrive in Britain in May before their early Champions Trophy exit was followed by a 3-0 Ashes series loss, made 143 in a total of 298 all out.
Together with Australia captain Michael Clarke (75), he shared a fourth-wicket partnership of 163, on a ground where they'd both played for Hampshire, after their side had slumped to 48 for three in this day/night clash.
Durham all-rounder Ben Stokes led England's attack with an ODI best five wickets for 61 runs, the 22-year-old all-rounder starring as Australia fell just short of 300.
England debutant Chris Jordan, in for fast bowler Steven Finn (side strain), took three for 47 after his first ball in international cricket was hit for four by Finch, whose last match on the ground saw him score a Twenty20 world record 156 against England last month.
But Australia had more than enough runs as they enjoyed a win over England ahead of the return Ashes series 'Down Under' starting in November.
"I'm extremely happy to win the series," said Clarke. "To a lot of people this ODI series does not mean much, but to the Australia players it means a lot.
"I don't know whether it will have much impact on the Ashes back home but we get the flight back home tomorrow (Tuesday) a lot happier as a one-day side certainly," the man-of-the-series explained.
"The Ashes is still a way away but everyone is excited about that and the players are thinking about it already, but our focus has to be on the seven ODIs in India first."
Man-of-the-match Watson added: "Things have changed for the better in a big way. We are playing the brand of cricket we enjoy and everyone is very excited about what lies ahead."
Meanwhile stand-in England captain Eoin Morgan, leading a side missing five rested Ashes-winners including regular skipper Alastair Cook, remained upbeat.
"We prioritise Test cricket and with back-to-back Ashes series we have to be picky and choosy. But the next best guys here have done really well."
England's reply got off to a disastrous start when Kevin Pietersen was run out for nought after being slow to answer Michael Carberry's call.
Carberry, on his home ground, made 30 before he was lbw to left-arm seamer James Faulkner (three for 38).
And it wasn't long before 50 for two became 68 for four as Joe Root (13) and Luke Wright (nought) came and went.
Morgan fell for 30 when stumped by Matthew Wade off spinner Adam Voges.
England's hopes now rested with Ravi Bopara and Jos Buttler, whose 65 not out saw them to a series-levelling three-wicket win in Cardiff on Saturday.
Buttler scored at better than a run-a-ball but Faulkner, cleverly changing to around the wicket, bowled him for 42 to end a stand of 92 with Bopara.
And when Bopara, who made 66, followed when well caught at extra-cover by Voges off Johnson to give the left-arm fast bowler his 200th ODI wicket, England were down and out at 197 for seven.
Pakistan-born leg-spinner Fawad Ahmed finished the match by bowling last man Rankin with two overs left.
Australia, on a ground where New Zealand's Martin Guptill struck 189 not out against England in an ODI in June, saw 48 for one become 48 for three when Stokes took two wickets in two balls after a 30-minute rain break.
Finch was caught by Morgan at point and next ball Matthew Wade gloved an intended hook to wicketkeeper Buttler.
Clarke, passed fit after fears he'd suffered a recurrence of his long-standing back injury, survived the hat-trick.
He followed his hundred in Australia's 88-run victory in the second ODI in Manchester with another fine innings before slicing a pull off Jordan to Pietersen at mid-off to end a 76-ball knock including 10 fours and a six.
Watson's dominant 107-ball innings, featuring 12 fours and six sixes, finished when he was caught behind off Stokes.