Stumps West Indies 268 for 8 (Cornwall 60*, Roach 4*, Lakmal 5-45) leadSri Lanka 169 by 99 runs
Until Rahkeem Cornwall joined Joshua Da Silva at the crease, Sri Lanka were in the game, with serious hopes of restricting West Indies to a lead of less than fifty. Suranga Lakmal had already claimed a five-wicket haul, all the specialist batsmen had been dismissed, and the second new ball was around the corner, with West Indies leading by just two runs.
But Cornwall, intent on proving he is a better batsman than his Test stats suggested, began to free his arms midway through the third session, hitting thumping blows down the ground, cracking seamers on the up, pulling ferociously, cutting on occasion, and generally imposing himself on the match in a manner that no batsmen had previously managed on this pitch. By day's end, he was not out on 60 off 79 balls - 48 of those runs having come from boundaries (nine fours, two sixes).
His 90-run eighth-wicket stand with Da Silva, who contributed only 29 to the partnership, broke the match open for the West Indies. Where before Cornwall's arrival it seemed as if the teams were in for a second-innings scrap, West Indies had achieved a commanding position by stumps - a triple-figure lead almost in hand. Cornwall had Kemar Roach for company at stumps, the team score at 268 for 8.
Sri Lanka's bowlers will feel, however, that the final scoreline on day two does not reflect their discipline, which had kept West Indies under significant pressure for the majority of the day. Lakmal was both the most potent and most persistent of Sri Lanka's operators, as he often is on foreign tours, and ended the day on 5 for 45 from 24 overs. Dushmantha Chameera bowled aggressively at times, and took 2 for 71, though thanks to his pace he was also the most hittable of Sri Lanka's frontliners. On a surface that offered only slow turn, Lasith Embuldeniya took 1 for 64, and kept an end tied while seamers attacked from the other.
Cornwall was somewhat watchful early on, playing out 15 deliveries before venturing a boundary, but when he arrived, he came like a storm. He smoked Suranga Lakmal past mid-off to collect his first four, before several overs later, he bludgeoned Vishwa Fernando to and over the deep midwicket boundary within the space of three balls. Sri Lanka had taken the second new ball by this stage, but that only made it disappear faster off Cornwall's blade. He rarely missed the chance to capitalise on errors on length, and although the feature of this innings was his boundary-hitting, Cornwall was not averse to working the singles on occasion. He reached his maiden half-century off the 62nd ball he faced. Da Silva largely ticked along sedately at the other end.
Before Cornwall hijacked the narrative, though, it had been Lakmal's day. He bowled a maiden first up, and then first ball of the second over, drew Kraigg Brathwaite into a loose shot outside off stump, the ball flying to second slip. The rest of his morning session was quiet, but he came in strong after lunch, bowling Jermaine Blackwood with his first ball of the session - a full, straight delivery that the batsman played all around. Several overs later, Lakmal also had Kyle Mayers (who had struck an effervescent 45) caught in the slips.
The two wickets to complete the five-for came after tea, as he bowled Jason Holder off an inside edge, before having Alzarri Joseph caught at point. This was his fourth five-wicket haul, the other three also having come away from home.
Before Cornwall, West Indies largely tiptoed their way through the day, respecting bowling that was frequently - almost uniformly - tight. John Campbell toiled his way to 42 off 132, forging a 56-run partnership with Nkrumah Bonner, who made 31. They were each dismissed either side of the lunch break, before Mayers injected some energy into the West Indies innings with his 45 off 70.
Mayers' innings was a little streaky - he edged his fourth ball past slip - but his aggression was calculated, and it shook West Indies out of the torpor that was threatening to overcome their innings at the time. Mayers hooked a Dushmantha Chameera bouncer for six over deep square leg against the wind, in the 43rd over, and would hit another six soon after, launching Dhananjaya de Silva's offspin over the sightscreen. He looked set to make West Indies' first half-century of the innings until Lakmal angled one in from wide of the stumps, bowling over the wicket, and got him to edge to second slip.
Mayers had got West Indies to within 40 runs of the lead, but it was Cornwall who rode West Indies into their excellent position. Sri Lanka's main hope now is that Cornwall's innings is an indication that the pitch has become much better to bat on.

Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. @afidelf