Root doubles up Sri Lanka
Joe Root hit a maiden Test double century before Sri Lanka reached 140-1 in reply to England's 575-9 declared on day two at Lord's.
Root turned his overnight 102 into 200 not out from 298 balls, including 16 fours, surpassing his previous Test-best score of 180 made on the same ground in last year's Ashes series.
England skipper Alastair Cook immediately waved in Root and last man James Anderson (9no), who had survived 15 deliveries to see his partner through to the milestone.
Opening batsman Kaushal Silva led Sri Lanka's response with 62 not out, although the tourists still trail by 435 heading into day three of the series opener.
Yorkshireman Root was the mainstay as England scored quickly after resuming on 344-5 at the start of day two.
Matt Prior missed out on a century, caught at short-leg off Shaminda Eranga's bowling for 86 to end a 171-run stand with Root, an England record for the sixth wicket in Tests between these two countries.
Seamer Eranga (3-163) also bounced out Chris Jordan (19) during an eight-over spell in which he went round-the-wicket as Sri Lanka tried a short-pitched mode of attack.
England had, by this point, reached 400 for the first time since the first innings in Wellington 15 months and 14 Tests ago and Stuart Broad rammed home that advantage with nine fours in his 38-ball 47.
Broad eventually holed out to midwicket off Nuwan Pradeep but Root and Liam Plunkett added 81 in 13 overs either side of lunch, England's record ninth-wicket stand against Sri Lanka.
Plunkett (39) became the fourth batsman to fall to the short ball when he miscued a pull to give Pradeep (4-123) his fourth wicket.
Root was on 181 when he was joined by Anderson, who got off the mark with a reverse sweep for four, wasted little time in collecting those 19 runs and brought up his double hundred with a dab sweep for two off spinner Rangana Herath (1-136) in mid-afternoon.
England's total was their highest against Sri Lanka, beating the 551-6 they made in the first innings at the same venue in 2006.
Sri Lanka opener Dimuth Karunaratne was reprieved by the DRS in Anderson's opening over after being given out lbw on the field. Hawkeye showed the ball was going over the top of the stumps.
He combined with Silva to see the tourists to 35-0 at tea, a partnership that had reached 54 when Jordan struck with his third ball in Test cricket.
Jordan (1-26), one of three England Test debutants along with Sam Robson and Moeen Ali in this match, had the left-handed Karunaratne caught behind for 38 driving at a delivery that drew him into the stroke.
England also thought they had Silva in the evening session after Broad (0-39) found his outside edge and wicketkeeper Prior claimed a low catch.
But Silva, on 39 at the time, stood his ground and replays were inconclusive as to whether the ball had carried into Prior's gloves.
He went on to complete his fourth Test half-century and remained there at the close alongside Kumar Sangakkara (32no).
Silva briefly had to keep wicket for Sri Lanka at the start of the day while Prasanna Jayawardene was having a hand injury, suffered during the warm-up, checked out. Jayawardene returned to the field and took the gloves back after missing just three overs.