Tillakaratne Dilshan hit 101 and took 3-37 to condemn England to a crushing 87-run defeat and seal a 5-2 series win for Sri Lanka.
Aged 38, the oldest player on the field marked his 300th one-day international with his 18th century to help the hosts to 302-6 in the final match in Colombo.
Dinesh Chandimal struck 55 not out and Thisara Perera flayed 54 off 26 balls.
Although Joe Root made 80 despite an ankle injury, England were bowled out for 215 with 4.1 overs unused.
The tourists never threatened to overhaul an imposing target, allowing Sri Lanka legends Mahela Jayawardene and Kumar Sangakkara to savour a comfortable victory in their final ODI on home soil.
Defeat was England's 11th in their last 15 completed ODIs, and leaves them palpably short of form and confidence with a maximum of five competitive matches - a triangular series against hosts Australia and India - before the World Cup starts in February.
The squad for the tri-series will be named on Saturday, but England's performances in Sri Lanka have done little to make the selectors' task easier.
Only twice in seven attempts did they pass 250, they were bowled out five times, they never fielded the same team two games in a row, and questions continue to be asked of captain Alastair Cook's place in the side.
"I would feel very wrong to walk away from it," Cook told Sky Sports. "If it's taken away from me, I'll feel very disappointed, but I certainly won't be giving it up."
Cook was dropped twice on Tuesday before he fell for 32, the third wicket in a top-order collapse to 78-5 from which England never recovered.
Moeen Ali was bowled first ball by off-spinner Dilshan, who had Alex Hales comfortably taken at long-on for seven.
After Cook edged Suranga Lakmal to slip, James Taylor gloved the seamer down the leg side and Eoin Morgan was lbw sweeping Dilshan.
Root, who turned his ankle while fielding, overcame obvious discomfort to take his tally for the series to 367 runs at an average of 73. Moeen was the only other batsman to score more than 185.
Root received fleeting assistance from Jos Buttler and Chris Woakes, who made 23 and 34 respectively, but the last four wickets tumbled for only 23 runs as England's tour ended on a sorry note.
Fittingly, Jayawardene and Sangakkara - the two greatest batsmen in Sri Lanka's history with a combined 824 ODI caps - completed the rout when they combined to stump Tredwell.
Root aside, no England batsman showed the application demonstrated by Dilshan after Sri Lanka chose to bat first on a pitch of little pace.
He struck nine fours and a straight six off 124 balls, and was largely content to play the supporting role in half-century stands with Jayawardene, Sangakkara and Chandimal.
Dilshan's departure in the 44th over - he swung a Chris Jordan full toss to deep mid-wicket - heralded the arrival of Perera, whose meaty half-century was central to Sri Lanka adding 93 in the last 10 overs.
(BBC)