De Silva and Rathnayake star in Sri Lanka revival against England
Sri Lanka were in dire straits at 6-3 after skipper De Silva won the toss, losing their first three wickets for no runs in 10 balls.
Yet they recovered to 236 all out, De Silva top-scoring with 74 and tailender Rathnayake, with only his third first-class fifty, close behind in making 72.
The pair checked England's progress during an eighth-wicket partnership of 63, with no other Sri Lanka batsman making more than Kusal Mendis's 24.
Chris Woakes struck twice in an over on his way to 3-32 in 11 overs.
De Silva's impressive innings ended when he turned a quicker ball from off-spinner Shoaib Bashir straight to Dan Lawrence at leg slip, with the 20-year-old taking 3-55 in 23 overs.
Ben Duckett and Lawrence, recalled in place of the injured Zak Crawley, guided England to 22-0 before bad light ended play for the day at 5:52 pm (1652 GMT).
Sri Lanka's initial collapse ensured a dream start for stand-in England captain Ollie Pope, leading his country for the first time after Ben Stokes was ruled out with a torn hamstring.
The tourists came into their first Test in England in eight years on the back of just a solitary warm-up fixture -- a defeat by the second-string England Lions -- with De Silva insisting Tuesday that Sri Lanka had wanted at least one more game before the series started.
"The conditions are quite different to Asian countries," he said. "We wanted to play a few matches, but that's what we get."
Stunning slump
Sri Lanka's collapse began in the sixth over when Dimuth Karunaratne top-edged a hook off fast bowler Gus Atkinson to wicketkeeper Jamie Smith.
Woakes then took two wickets in the next over, with Nishan Madushka, the other opening batsman, driving loosely at an outswinger and edging to Joe Root at first slip as he fell for four.
Five balls later, Angelo Mathews was plumb lbw for a duck playing no shot to a Woakes delivery that nipped back off the pitch.
Mendis was undone by express fast bowler Mark Wood, with Mendis gloving a superb 93 mph (150 km/h) delivery that reared up from short of a length to second slip.
De Silva, however, pulled Atkinson for a commanding four and completed an impressively quick fifty off just 56 balls.
He was reprieved on 65, when Smith missed a difficult stumping chance off Bashir, but was out shortly afterwards to leave Sri Lanka 176-8.
But the 28-year-old Rathnayake, undaunted by the loss of his skipper, went to a 96-ball fifty in style when the left-handed batsman drove Bashir for a straight six that also took Sri Lanka past 200.
With the floodlights piercing increasingly gloomy skies, Pope turned to part-time spinner Root in a bid to snatch a wicket at a time when deploying the fast bowlers might have seen the umpires halt play for bad light.
Rathnayake, however, responded by launching Root for six over long-off. He also drove Bashir through extra cover before hitting him to Woakes at mid-on.
Before play started there was a minute's applause in honour of Graham Thorpe, the former England batsman and assistant coach, with both teams, as well as the match officials, wearing black armbands in his honour.
Thorpe died aged 55 earlier this month after being hit by a train. His wife Amanda confirmed he had taken his own life having suffered from depression for several years.
