Two late tries from Colm Reilly and Thomas Clarkson secured Ireland a 26-17 win over Wales and their first Grand Slam since 2007, a magnificent achievement considering they haven't finished higher than third in the table since last winning the U20 Six Nations title in 2010.
Shorn of talismanic half-backs Harry Byrne and Craig Casey and captain David Hawkshaw through injury, Ireland found it tough going in the first half and they trailed by 10 points at the break.
Jonathan Wren's try just before half-time saw Ireland reduce the deficit to three points, having gone behind to Aneurin Owens' 11th-minute try with Cai Evans, son of Welsh rugby great Ieuan Evans, kicking a conversion and a penalty.
Dylan Tierney's fourth try of the championship, converted by Ben Healy, put Ireland in front for the first time in the 47th minute but the home side quickly hit back with seven points of their own to edge in front, Evans converting Jac Morgan's try as the hour-mark approached.
Chasing their first win in four visits to the North Wales venue, Ireland piled on the pressure and found a way to win, a quality that will serve them well at the upcoming World Rugby U20 Championship in Argentina.
Ireland stung Wales with a terrific late two-try salvo, Reilly scampering over in the 72nd-minute and ever-present tight-head Clarkson muscling over right at the death to start the celebrations.
Defending Six Nations and world champions France had to settle for second place after seeing off Italy 35-31 in a tremendous game of rugby in Biella. Both teams scored five tries apiece, the difference being France were successful with all their conversion attempts while Italy missed two.
After conceding an early an unconverted try to Azzurrini full-back Jacopo Trulla, France hit back with scores from Kevin Villiard and Maxence Lemardelet which were both converted by Mathieu Smaili for a 14-5 half-time lead.
Lively winger Vincent Pinto and Ethan Dumortier added two more tries within four minutes of the restart but just as it looked as though France would pull away, Italy responded with a pair of tries from hooker Andrej Marinello.
France were starting to look nervy but they regained their composure to manufacture a fine try from Yoram Moefana, which Smaïli converted.
Still, it was Italy who finished the stronger, as Michael Mba scored twice, including with the final play of the game, but time was against them and France held on.
England claimed their third win of the campaign, and third place, after turning in a powerful second-half performance to beat Scotland 45-7 at Franklin's Gardens in Northampton.
Despite Scotland taking an early lead via Cameron Anderson’s converted try, England led 12-7 after a disjointed first half with tries from Tom de Glanville, son of former England captain Phil, and Tom Willis.
A much-improved display after the break brought five more tries and 32 unanswered points as Steve Bates' side ended a mixed campaign in style.
England had to wait until the 56th minute, however, before extending their lead, De Glanville turning provider on this occasion as he helped set up a try for Aaron Hinkley.
Four more tries then followed in quick succession, Cameron Redpath, replacement Alfie Petch and Alfie Barbeary all crossing before Arron Reed closed out a comfortable victory with a length-of-the-field effort.
Photo: INPHO/Ryan Byrne