The triple crown belongs to Ireland. The champions’ grand slam attempt remains alive, and Simon Easterby’s supremely well-drilled team are on course to claim a historic third successive Six Nations title.

They had a serious scare under the roof in Cardiff, though, thanks to a sensational performance by Wales under their interim head coach Matt Sherratt. Since being hurriedly appointed last week, the Cardiff head coach had only four training sessions to implement his ideas, and has made a remarkably positive impact.

Related: Matt Sherratt hails his Wales players’ ‘emotion and ambition’ despite defeat

Ellis Mee, the 21-year-old Welsh debutant, was denied a potentially decisive try in the final 10 minutes by a fiendishly tight call by the television match official. Ireland ultimately edged over the line, with the fly-half Sam Prendergast’s kicking instrumental in the final quarter. But they were frequently forced on to the back foot by a magnificent Welsh effort after 14 consecutive Test defeats under Warren Gatland. That run now stretches to 15, but the pain of this loss was considerably sweeter.

Sherratt had torn up Gatland’s script and selected a Gloucester-heavy back line with familiarity – AKA cohesion – the objective. Born in the west of England, Sherratt spoke during the week of once being called an “unknown little Englishman” by a fan on social media. Much more of this and he will surely be promoted to honorary Welshman.

His team looked better from the start. An early scrum penalty was followed by a fluent first possession, but when Jack Conan turned it over, Garry Ringrose’s delightful 50:22 put the hosts under pressure. Neatly enough, it was Conan who eventually scored from close range, man-handling Tomos Williams, the Wales scrum-half, as he went over the line.

Unlike Scotland at Murrayfield a couple of weeks ago, however, Wales succeeded in preventing Ireland from getting the scoreboard spinning like a fruit machine. The hosts’ attacking shape was an entirely different proposition, with willing runners catching fizzing passes on the move, and Gareth Anscombe’s penalty soon got them off the mark.

That old Principality Stadium roar swelled further when more slick handling saw Wales puncture the Irish defence on the right. Jac Morgan fed a pass inside to Tomos Williams, who contracted a bad case of try-line fever.

Sherratt’s front-row selection was bearing fruit, with three scrum penalties against Ireland inside half an hour. The visitors had even more to reflect on when Ringrose was shown a ­yellow card, including a bunker review, for a reckless head-on-head challenge on Ben Thomas.

Anscombe slotted the penalty and a reinvigorated Wales continued to work through some impressive attacking phases, the 6ft 4in Mee looking a Test-match natural. Even when Mee knocked on with Wales on the attack, it worked out OK, a fourth scrum penalty against Ireland arriving.

That penalty led to a thrilling passage of play with Ireland somehow repelling Wales twice when carriers looked over the try-line. Captain Morgan finally barged over, provoking an earth-trembling roar. Anscombe’s conversion meant Wales led by three at the break. A woman carrying a tray of pints back from the bar refused to believe a steward when informed Wales were winning 13-10.

That tray of drinks, presumably, went flying three minutes after half-time when Wales broke with devastating efficiency, Tom Rogers diving spectacularly to score in the righthand corner after being fed by the full-back Blair Murray. Remarkably Wales led by eight. The official Six Nations website, pre-match, had given them a 9% chance of victory. One bookie had Ireland at 1-50 to win.

France are seeking a reaction to their defeat by England as they look to reignite their Six Nations title push in Rome on Sunday. Fabien Galthié has responded to the 26-25 loss at Twickenham by making seven changes, including dropping the star wing Damian Penaud and the fly-half Matthieu Jalibert.

Thomas Ramos shifts from full-back into the No 10 jersey and Galthié has sprung another surprise by naming a seven‑one split between forwards and backs on the bench.

The wing Simone Gesi and the hooker Gianmarco Lucchesi are the new faces in Italy’s team as they look to follow up their victory over Wales. The hooker Giacomo Nicotera said: “We can’t say: ‘We’ve beaten Wales, that’s it.’ The objective is to beat a team that is better than Wales.” PA Media

Ringrose’s yellow was then upgraded: why such an obviously reckless challenge did not warrant a straight red is a question for Christophe Ridley and his officials.

Related: Wales 18-27 Ireland: Six Nations – live reaction

Prendergast narrowed the gap to five with a penalty; the fly-half had coughed up an error or two early, as he had in the opening win against England, but again he grew into the game. The Leinsterman produced a stunning kick for touch to set up the levelling score. James Lowe cleverly patted a high kick back inside for Jamie Osborne and it was all square.

Ireland tightened their grip and three further Prendergast penalties made it 17 points for him in total – enough to keep Ireland’s campaign on track, despite Mee’s spectacular diving attempt that was denied by the TMO after a long, tense wait. France visit Dublin in two weeks for their biggest test. Wales go to Scotland with pride emphatically restored.