Sri Lanka 29 for no loss (Oshada 21*, Karunaratne 7*) and 506 beat Bangladesh 169 (Shakib 58, Asitha 6-51) and 365 by 10 wickets
Asitha Fernando's searing post-lunch spell burst through Bangladesh's defiant middle order, then swiftly uprooted the tail, to thrust Sri Lanka toward victory, which they achieved by 10 wickets in Mirpur. Envenomed by reverse swing, Asitha engineered a collapse that saw the last five Bangladesh wickets fall for 13 runs in the space of eight overs.
He took 6 for 51 for the innings - easily the best innings return of his five-Test career. As he had claimed four wickets in the first innings as well, he took 10 for 141 from the match. This is his first 10-wicket haul.
Following Asitha's burst, Sri Lanka needed only 29 in the fourth innings. Oshada Fernando struck a nine-ball 21 to complete the win inside three overs.
Bangladesh had defied Sri Lanka through a 103-run stand between Shakib Al Hasan and Litton Das, but of course were battling a 141-run first-innings deficit, and already suffered a top-order collapse. In the end, all a partnership of even this quality could do was stave off an innings defeat. Shakib was the aggressor through this partnership, reeling off seven boundaries in a 72-ball 58. Litton made 52 off 135.
And it was Asitha's dismissal of these two batters that essentially secured Sri Lanka's victory. He dived hard to his right in his follow through to intercept a low chance from Litton. The wicket of Shakib soon after was more impressive. Having delivered excellent bouncers right through the series, he rushed Shakib into a hook shot, with the ball ballooning up off the batter's gloves, to the wicketkeeper. He then got Taijul Islam lbw with a full, reverse-swinging delivery, and knocked back Khaled Ahmed's middle stump to end Bangladesh's innings.
At the other end, Ramesh Mendis spun one into the pads of Mosaddek Hossain, who missed a lap sweep and was ajudged lbw. This was the only wicket the Sri Lanka spinners claimed throughout the whole match. Asitha and Kasun Rajitha, who removed the dangerous Mushfiqur Rahim earlier in the day, claimed 17 wickets between them.
In the 90 minutes before lunch, however, Shakib and Litton had given Bangladesh some semblance of hope. They had begun the day four wickets down and still 107 runs back, but Shakib's adventure in particular seemed to have blunted the Sri Lanka attack slightly.
Shakib had been immediately aggressive at the crease, thumping his fifth ball - from Rajitha - to the cover boundary, before cutting him behind point, then hitting another boundary through the covers later in that same over. He rarely let bowlers deliver dot balls at him, finding singles almost at will. And when they erred in length, Shakib pounced, pounding that cover boundary with particular relish. All but two of his seven boundaries came in that area.
Litton, meanwhile, had successfully overturned a caught behind decision on 9, and was more conservative than Shakib, though he too made sure to score off the bad balls. He had been rapped on the pads and was somewhat streaky in the early overs, but appeared much more assured in Shakib's company, rotating the strike effectively when the spinners were in operation. Late in the morning session, he completed 2000 career runs.
Sri Lanka's only breakthrough in the extended morning session (they had started half an hour early to make up for a rained-out session on day three), was the result of an excellent Rajitha delivery. The ball having been angled into Mushfiqur, kept low upon pitching, and skidded into off stump before Mushfiqur could get his bat down.
The win in Mirpur pushes Sri Lanka up to fourth on the World Test Championship table, after three series played. Bangladesh remain at No. 8, with just one Test win across their four series thus far in the cycle.
Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. @afidelf