Cardiff: Joe Root struck a measured 93 as England completed their series win over Sri Lanka with a 122-run victory in the fifth one-day international at Cardiff.
Root's 106-ball innings helped England to 324-7 as he also shared a century stand with Jos Buttler (70).
Liam Plunkett (3-44) and David Willey (4-34) then ensured Sri Lanka were all out for 202 with 7.2 overs left.
England move above Sri Lanka to fifth in the ODI rankings, and look a different side to the one that exited last year's World Cup at the group stages.
In the run chase, Gunathilaka's 48 proved useful after some early wickets, but his dismissal to Plunkett meant only Dinesh Chandimal could provide some resistance with 53 until he was bowled by Willey.
On a pitch that had looked to favour seam bowling, spinner Adil Rashid picked up 2-41 in his 10 overs, as Willey returned late on with two 41st-over wickets before finishing off the visitors in his next set.
Earlier, England managed to put up a huge total. They were able to score 324 for 7 in 50 overs with efforts from Joe Root (93), Jos Buttler (70) and James Vince (51).
England were off to a decent start as Jason Roy and James Vince shared a partnership of 67 before Roy played a loose shot to get caught in the deep.
Root joined Vince in the middle. Soon after Vince completed his maiden ODI fifty. He got stumped out as he came dancing down the wicket trying to hit the ball over the bowler’s head. He was joined in the middle by skipper Eoin Morgan after Vince gave his wicket away.
Eoin Morgan reached a new feat in the fifth ODI as he reached 100 ODI sixes for England as he becomes the first to do so for the side.
He got out for 20 after playing himself in trying to loft the ball over cover region.
Bairstow came in the middle and tried to form a partnership with Root. His wicket was also a soft dismissal as he chipped the ball straight to long-on fielder as Gunathilaka picked up his third wicket.
Buttler and Root shared a partnership of 109 to take England out of danger.
They tried to rotate strike when spin came into play trying not to loose their wickets. Buttler reached his half century hurriedly, hitting boundaries all over the park. He scored 70 runs before his stumps were shattered by debutant Bandara who picked up his first wicket in ODIs.
England finish with a 3-0 series win, while Sri Lanka are winless on their tour with a Twenty20 left.
Brief scores
England - 324 for 7 (Root 93, Buttler 70, Vince 51, Gunathilaka 3-48)
Sri Lanka - 202 (Chandimal 53, Willey 4-34, Plunkett 3-44)
Result - England won by 122 runs