England edged Ireland 13-10 in a test of breathless intensity at Twickenham to open up the Six Nations into a four-team race at the halfway point on Saturday.
Ireland was the last unbeaten side in the championship after France fell to Wales on Friday, and was favoured to end a three-match losing run to England with a side with more than twice as many caps, rampant momentum, and added incentive to celebrate Brian O'Driscoll's world record-tying 139th test cap.
But England, with unexpected daring, overturned a 10-3 deficit to lead again within eight minutes, and more than a quarter of the match to go.
In a match marked by gritty, desperate defence, the young English withstood a firestorm finish from Ireland to register what coach Stuart Lancaster called the best win in his tenure, considering the context.
``Given the experience of the Ireland team, the form they were in, the quality of the coaching and the players they've got and some of the relative inexperience we have, I'm just so proud of the boys,'' Lancaster said.
``We showed great maturity in closing out the game. It was character, spirit, playing for the shirt. Ireland, fair play to them, threw everything at us, and once we got that lead we just clung on in there.''
Four teams were tied at the top, with Ireland ahead only on points difference from England, Wales and France.
The next decisive matches appeared to be England hosting two-time defending champion Wales in two weeks, and France closing the tournament at home against Ireland.
``Our points differential puts us in a good position, so we've got to make sure that we go forward to Italy as opposed to looking back too much at this game, because we've got to take some positives from it,'' Ireland coach Joe Schmidt said.
``A lot of people were saying that we wouldn't get a result here and you can't come too much closer to getting a result than a small one score, so I feel really sorry for the players because they put a lot of effort in. At the same time, I have a lot of respect for what England managed to deliver.''
England and Ireland scored one converted try each, with the difference on the scoreboard provided by England's Owen Farrell, who knocked over two of his three penalty attempts. Jonathan Sexton hit the only penalty shot he had.
Ireland's scrum was dominant, taking advantage of England tighthead David Wilson playing with only a half of rugby in two months. But for all of the ball Ireland had, it couldn't turn pressure into points as England's defence and discipline was top shelf.
England fired the first shot in the thriller. Left wing Jonny May should have crossed in the right corner early but he was slowed by Ireland flanker Peter O'Mahony and scrumhalf Conor Murray arrived just as May was diving over the line to knock the ball from his grasp.
Then Ireland worked a brilliant move, with Sexton's crosskick caught by Andrew Trimble on the right wing, but his offload inside was bobbled by fullback Rob Kearney, who was swallowed by Englishmen.
Farrell was lucky soon after not to be sin-binned. His late shoulder charge on Murray conceded only a penalty. Referee Craig Joubert's decision was critical, because Farrell then kicked the only points of the half, a penalty from 50 metres.
Farrell's second penalty chance hit the upright, and the teams could both be happy where things stood at the break.
Just 90 seconds into the second half, Ireland was even happier.
Ireland worked lineout ball to the middle of England's 22, No. 8 Jamie Heaslip stood wide of a ruck and England believed he was spreading it wide. He was waiting for Kearney to scream up inside him, slice clean through and curve towards the posts untouched.
Sexton converted for 7-3, and added a penalty in the 49th for 10-3.
Then England turned on the pressure, and Ireland was happy to concede three points rather than five. Farrell obliged and the deficit was four.
England's try came from surprising ambition inside its own half. Farrell, under pressure in space, could have kicked the ball for relief but passed to Jack Nowell, who found Mike Brown inside speeding into a gap on halfway. Brown blew through, and scrumhalf Danny Care came up his inside to finish off between the posts. Farrell converted, England had the lead back, and this time kept it.
O'Driscoll, playing England for a 13th and final time before retiring after the season, limped off with minutes to go, and was in the stands as Ireland's Triple Crown and Grand Slam hopes evaporated.