Sam Robson scored his first half-century for England on day two of the second Investec Test against Sri Lanka but captain Alastair Cook suffered another disappointment.

Robson, who endured a tough debut at Lord's, reached lunch on a hard-working 55 not out in England's 106 for one, with Gary Ballance unbeaten on 30 at Headingley.

That left England promisingly positioned in response to the tourists' 257 all out, but there was one significant negative.

Cook, who has gone 23 innings and 13 months since his last Test hundred, added just three runs to his overnight score of 14 before nicking Dhammika Prasad to first slip.

He had spoken before the game about the need to silence his doubters with an innings of substance but the tentative nature of his dismissal, pressing forward half-heartedly and edging a full delivery, was quite the opposite.

Robson started the day by taking 10 runs off Prasad's first over, including a slightly streaky top edge over the slips and a tidier flick to fine leg.

Cook scored off his eighth ball of the morning, working Shaminda Eranga for three into the onside, but that was as good as things got for the left-hander.

He was gone to the first ball of the fourth over, indecisively leaning into a full Prasad delivery and sending a low catch to Kumar Sangakkara at slip.

That brought Robson and Ballance together, a pair with just three Test caps between them prior to this game.

And while Ballance celebrated his maiden Test century at Lord's, Robson came in having made scores of one and 19.

Both men set up conservatively, though Prasad offered Ballance the chance to get off the mark with a cut for four.

With an hour gone England were 68 for one, with Ballance reeling off a couple of boundaries after drinks to liven the crowd.

Robson ended a period of relative inactivity when he successfully threaded Nuwan Pradeep for four past gully and two balls later produced a pleasing drive to the extra-cover boundary.

That brought him within sight of 50 and he reached the landmark with a thick edge wide of second slip from his 102nd ball.