Jack Leach fell eight short of becoming the first England nightwatchman to make a Test century, but Ireland retained the upper hand in their maiden Test at Lord's.

While Leach and Jason Roy were together in a second-wicket stand of 145, it seemed England may set an intimidating fourth-innings target for Ireland. But once they were parted, England lost seven wickets for 77 runs to present Ireland with a wonderful opportunity to mark their trip to Lord's with a historic win.

It says something for the struggles of England's batsmen of late that they were grateful for the contribution of Leach. He came into this match averaging 4.66 in the County Championship season, having made just 42 runs in 12 innings, with some at Somerset fearing his confidence had been permanently damaged by a blow on the head while batting against Morne Morkel last year. He came in at No. 11 in the first innings.

While he was being beaten like a snare drum in the opening overs of the day, it seemed unthinkable that he would contribute anything too significant here. But he got off the mark with a thick edge off Tim Murtagh that flew between slips and gully and was then grateful for four overthrows after his quick single was rewarded by a deflection off the stumps to the boundary; not the first time a deflected throw has come to England's aid on this ground in recent times.

And, slowly, he began to settle. With the ball softening and the attack tiring in draining conditions - the temperature hovered around the mid-30s throughout the day - Leach began to believe he could move on to the front foot without much fear and, as a consequence, started to unveil a series of surprisingly elegant drives. At one stage he hit five fours in nine balls - including three in four off Boyd Rankin - with some languid straight and cover drives especially eye-catching.

His fifty came with his eighth boundary - another thick edge - off 82 balls and, a short while after lunch, he exceeded his previous first-class career best of 66.

He gave two clear-cut chances. On 72 he fenced at a short ball from Rankin only to see Gary Wilson, the Ireland keeper, put down a straightforward chance (you wondered whether the watching Theresa May sympathised; she had Irish backstop issues of her own) before, on 92, he was dropped at second slip by Mark Adair as he pushed at one from the admirable Murtagh.

But Adair made amends three balls later and Leach was left eight short of a place on the Lord's honours board. He joined Alex Tudor, Harold Larwood, Eddie Hemmings and Jack Russell in making it into the 90s as a nightwatchman for England - Tudor's 99 not out in 1999 remains the highest. Leach can, at least, console himself with the knowledge that he is believed to be the first nightwatchman in history to make a Test half-century as an opening batsman. He is also just the second man, after Harry Butt, to bat at No. 11 and open on the same day of a Test.

His contribution also dwarfed most of those made by England's regular openers in recent times. Indeed, Leach's score was the second highest - following Keaton Jennings's century in Sri Lanka - by an England opener since the retirement of Alastair Cook in September. England's openers recorded just three half-centuries between them in the six Tests played over the winter.

Leach was given increasingly assured support by Roy. While there were some nervous moments early in his innings - one attempted flick through midwicket resulted in a thick edge that passed just out of reach of the slip cordon - he looked increasingly like the white-ball version of himself and was merciless on anything short, wide or over-pitched.

He greeted the introduction of Andy McBrine's offspin from the pavilion end by skipping down the pitch and heaving his second delivery over midwicket for six. A short while later, a fierce sweep for four brought up England's hundred. Shortly before lunch, he completed the quickest half-century by an England debutant in Test history. Roy reached the milestone in 47 balls; Matt Prior took 55.

At one stage, with England 49 ahead and nine wickets in hand, it seemed Ireland may have missed their chance. But the wicket of Roy, his big drive beaten by a Stuart Thompson inswinger, precipitated a collapse. Adair, nipping the ball both ways, had Jonny Bairstow leg before to complete his pair ("Jonny Pairstow", the Twitter wags called him), Joe Root acrobatically caught behind as he tried to drive one that left him and Chris Woakes caught in the slips as he drove lavishly at an outswinger.

Moeen Ali's grim form with the bat continued as he fenced at a Boyd Rankin bouncer, while Joe Denly was sold short by his captain after he was called and then sent back for an improbable single.

By the time Woakes departed, England's lead was a modest 126 and they had only two wickets in hand. But Sam Curran counterattacked in typically flamboyant fashion - there were four fours and two sixes in his 29-ball stay - to add 45 for the ninth wicket with Stuart Broad, whose own pull for six took England past 300. It may yet prove a crucial contribution. With one wicket in hand, England led by 181 when lightening forced an early conclusion to play with more than 20 overs unbowled.

Still, England have now made 400 only once in their previous 32 Test innings and not at all in their previous 14. Only once in those 14 innings have they reached 350. Four times in the last seven innings, they have failed to reach 200. On the eve of the Ashes, those are statistics that will have the England management worried.

Such issues can wait. Ireland will go into the third day of their third Test with a wonderful chance to seize a win that, ahead of the match, their captain William Porterfield suggested would register as the greatest achievement in the history of Irish cricket.