England seized control of the third Test with Sri Lanka on Saturday to move within sight of a series whitewash, but will anxiously await further news on an injury to captain Alastair Cook.
Having resumed in a strong position on 162-1 in reply to England's 416, the tourists collapsed to 288 all out on day three, Chris Woakes and Steven Finn each finishing with three wickets.
Cook was unable to open the batting when England began their second innings, having been dealt a painful blow to the knee while fielding at silly point shortly before lunch.
An X-ray showed the England captain had avoided a fracture, but he will be assessed again on Sunday morning, when his team are set to resume on 109-4, holding a healthy lead of 237 on a pitch beginning to offer variable bounce.
Nick Compton, promoted to open in Cook's absence, fell for just 19 and may well have played his final Test, while Nuwan Pradeep (3-25) removed Joe Root (4) and James Vince (0) with successive balls to leave England wobbling on 50-3.
However, the in-form Jonny Bairstow followed up his first-innings 167 by adding a handy 32 and Alex Hales ended the day unbeaten on 41 - having twice been dropped - to ensure the hosts reached stumps firmly on top.
Sri Lanka had impressed with the bat on day two, but got off to a miserable start on Saturday, losing three wickets for seven runs.
Kusal Mendis and Kaushal Silva failed to add to their respective overnight scores of 25 and 79, falling victim to Woakes and Stuart Broad respectively.
Woakes, who removed Mendis with his first ball of the day, then found some extra bounce to have Angelo Mathews (3) held at second slip by Root.
Finn got in on the action by removing Dinesh Chandimal (19) and Lahiru Thirimanne (17) in successive overs prior to lunch, while Root was pressed into captaincy duty for the afternoon session following Cook's injury.
Although Kusal Perera (42) and Rangana Herath (31) offered resistance with a partnership of 71, the latter's departure to Broad prompted another collapse and Sri Lanka's last three wickets fell without addition to the score.
Following an early tea, England strengthened their position through Hales and Compton, but the latter was unable to end his run of low scores and edged behind off Shaminda Eranga to end an opening stand of 45.
Pradeep soon cleaned up Root with one that kept very low, before bowling Vince, who misguidedly shouldered arms to the next ball.
Bairstow was also bowled by the impressive Pradeep late in the day, but Hales - spilled at second slip by Dimuth Karunaratne on 19 - survived a second chance, this time to Chandimal, as he and nightwatchman Steven Finn (six not out) survived a nervy end to the day.