England extended their winning run to 16 Tests as wing Elliot Daly's late try clinched a dramatic RBS 6 Nations victory over Wales in Cardiff.
The first defeat of Eddie Jones' coaching reign appeared to be looming large as Wales led by two points with four minutes left, but Daly finished off brilliantly following a poor Jonathan Davies clearance, and Owen Farrell's conversion saw England home 21-16.
Wales looked to have done enough to end England's Grand Slam hopes as wing Liam Williams scored a first-half try and full-back Leigh Halfpenny kicked 11 points.
England led through a Ben Youngs touchdown, while Farrell also booted two penalties, but they had to dig deep into their resources before ultimately prevailing.
It was a first defeat in five games for Wales under interim head coach Rob Howley, who is in charge this season while Warren Gatland concentrates on British and Irish Lions business, but England made it four Six Nations wins in a row at their hosts' expense.
A pulsating contest packed with huge defensive work by both sides and a willingness to move possession wide kept a capacity Principality Stadium crowd engrossed throughout.
It remained in the balance until the dying minutes, but proved a tale of heartbreak for Wales as all their hard work was undone by Daly.
Wales showed two changes from the side that saw off Italy in Rome last weekend, with wing Alex Cuthbert replacing leg injury victim George North, while props Rob Evans and York-born Exeter tighthead Tomas Francis also started as the home team targeted a fifth successive victory under Howley.
There were two switches in the England side following a tense battle against France, as wing Jack Nowell replaced Jonny May and Harlequins flanker Jack Clifford took over from Tom Wood. England's back row had a combined total of just 20 caps, compared with Wales' 130.
And Wales blasted out of the blocks, dominating territory either side of a third-minute Halfpenny penalty, while also claiming two possession turnovers as England's battering ram number eight Nathan Hughes twice found himself knocked backwards in the tackle.
Farrell put England level after Wales number eight Ross Noriarty was penalised, and the visitors began to find impressive rhythm, using strong ball-carriers like Nowell and flanker Maro Itoje to strong effect as Wales were tested defensively.
And Wales could only hold out until the 18th minute as England moved possession wide and at pace, before a ruck close to the line resulted in Youngs touching down underneath a pile of bodies.
Farrell missed the angled conversion attempt, yet, while England had served notice of their impressive forward power, Wales kept chipping away as a second Halfpenny penalty cut the deficit to two points.
Wales fly-half Dan Biggar then broke clear, tussling with Nowell before England cleared the danger, but only after Biggar's half-back partner Rhys Webb was inches away from touching down during a fast and furious contest.
The hosts kept hammering away deep inside England's 22, only to be denied again when Webb's pass to Alun Wyn Jones bounced off the skipper and behind him.
But Wales finally broke through, courtesy of a training-ground move, as Ross Moriarty fired quick scrum ball to Webb, before Liam Williams cut a brilliant angle, running between England centres Farrell and Jonathan Joseph, before Nowell's intervention was too late to prevent a try.
Halfpenny added the conversion, and Wales trooped off 13-8 ahead, putting England under severe pressure for the second period if they intended extending their long unbeaten run.
Wales resumed the game in determined fashion, with Moriarty making crunching tackles on Farrell and Maro Itoje in quick succession, before centre Davies set up a flowing move that ended inside England's 22.
Jones soon began using his bench, replacing captain Dylan Hartley with Jamie George and sending on James Haskell for Clifford before 10 minutes of the second half had elapsed, and a second Farrell penalty made it 13-11.
A Halfpenny strike following relentless Wales pressure restored a five-point gap, and, after England pushed hard for another try, the home side broke clear when Biggar intercepted Youngs' pass and sprinted clear, but Daly got back in the nick of time.
And that set the scene for a thrilling finale following another Farrell penalty, with Daly applying the killer blow to Wales and Farrell adding the extras.