Second-row Cory Hill forced his way over in the 68th minute after a lengthy period of Welsh resurgence to seize the lead for the first time, his team thriving amid the arrival of replacement fly-half Dan Biggar from the bench to direct the final quarter.
And bedlam ensued at the Principality Stadium in the closing moments when Josh Adams grabbed Biggar's crossfield kicked to touch down and confirm a famous win.
Gatland's first taste of success over opposite number Eddie Jones in four attempts also set a new national record of 12 consecutive victories and was a fitting way to end their Championship rivalry before the Kiwi steps down after the World Cup.
Follow post-match reaction below:
Good morning and welcome to The Independent's live coverage of today's Six Nations clash between Wales and England, brought to you from pitchside at the Principality Stadium.
In a clash between the two remaining unbeaten sides of the tournament, the Grand Slam is on the line as these two fierce rivals collide from 4.45pm.
Warren Gatland and Eddie Jones have been vocal in their rivalry this week to build up tensions ahead of kick-off, and with the winner of the grudge match set to go on and challenge for a rare Grand Slam, there is plenty on the line in this weekend's big encounter.
We'll begind out live coverage from 3pm, with France vs Scotland set to kick-off the action today at 2:15pm.
It's fair to say that the streets of Cardiff are buzzing this afternoon.
There are thousands in the pubs and bars around the Principality Stadium, and you can guarantee they'll be well oiled come kick-off.
That's lukcy because they face quite the wait to get into the stadium, with new security measures introduced causing quite the wait outside for fans. Organisers have been vocal in this to get fans inside early enough for kick-off, but such is the activity levels outside that many are probably going to leave it too late.
After making the journey along the M4 this morning, thankfully the thick fog that lined the motorway and much of London has lifted over the Welsh capital, making way for a lovely sunny day in Cardiff.
With the roof open, that will play into an attacking game, although England could look to try and take that speed and flare out of the encounter with their tactical kicking - just as they did against Ireland and France.
So much was made of yesterday's late journey down to Cardiff, but we can report that the England coach has arrived safe and sound, skipping the traffic in the process with a police escort.
Just an hour to go until kick-off here in Wales, and after peeking an eye at the score in today's first match (which France are leading 15-3 and worth every point of their lead) preparations here in Cardiff are beginning to reach a climax.
Wales have arrived at the ground along with England, and while we're yet to hear confirmation, the rumour is there's no changes to the sides as announced.
So what will prevail today: the passion and emotion of the Welsh, or England's cool, calm and calculated approach to silencing the crowd?
Owen Farrell spoke ahead of the weekend of why he believes England will be ready for anything Wales throw at his side.
Here's how the two teams line up today:
Wales: Liam Williams (Saracens); George North (Ospreys), Jonathan Davies (Scarlets), Hadleigh Parkes (Scarlets), Josh Adams (Worcester); Gareth Anscombe (Cardiff Blues), Gareth Davies (Scarlets); Rob Evans (Scarlets), Ken Owens (Scarlets), Tomas Francis (Exeter); Cory Hill (Dragons), Alun Wyn Jones (Ospreys); Josh Navidi (Cardiff Blues), Josh Tipuric (Ospreys), Ross Moriarty (Dragons).
Replacements: Elliot Dee (Dragons), Nicky Smith (Ospreys), Dillon Lewis (Cardiff Blues), Adam Beard (Ospreys), Aaron Wainwright (Dragons), Aled Davies (Ospreys), Dan Biggar (Northampton), Owen Watkin (Ospreys).
England: Elliot Daly (Wasps); Jack Nowell (Exeter), Henry Slade (Exeter), Manu Tuilagi (Leicester), Jonny May (Leicester); Owen Farrell (Saracens), Ben Youngs (Leicester); Ben Moon (Exeter), Jamie George (Saracens), Kyle Sinckler (Harlequins); Courtney Lawes (Northampton), George Kruis (Saracens); Mark Wilson (Newcastle), Tom Curry (Sale Sharks), Billy Vunipola (Saracens).
Replacements: Luke Cowan-Dickie (Exeter), Ellis Genge (Leicester), Harry Williams (Exeter), Joe Launchbury (Wasps), Brad Shields (Wasps), Dan Robson (Wasps), George Ford (Leicester), Joe Cokanasiga (Bath).
Referee: Jaco Peyper (South Africa).
Assistant referees: Jerome Garces and Alexandre Ruiz (both France).
The choirs are booming out around the Principality Stadium, with the hymn Calon Lan taking everyone back to 2017 when both sides were singing in unison on the Lions tour.
But there will be no friendly faces today. Every England name is booed as it is read out, every Welsh name cheered to the rafters.
Warren Gatland ahead of kick-off to the BBC:
It'll be a tough game and I'm expecting it to be a close call, nothing will be comfortable out there.
Their kicking game. They've kicked a lot from their first two games and they've had a lot of success from it, so I expect more of the same.
A taste of the pre-match atmosphere:
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