We look at the key talking points after Saturday's Six Nations results, with Steve Borthwick's England failing to click, Scotland firmly in the title mix, and Ireland going for history...
Where to next for Borthwick's England?
What to make of England under Steve Borthwick? Their Round 4 fixture vs Ireland will be his 20th Test in charge, and while some will point to a third-placed finish at the World Cup, in a wider context his record so far is hard to read as anything other than woeful.
Since taking charge in December 2022, Borthwick's side have played Scotland twice and lost both, played Ireland twice and lost both, played France once and lost by a record margin at Twickenham, and he has become the first England head coach ever to oversee a defeat to Fiji.
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Their only Six Nations victories have come vs Wales twice and Italy twice - fifth and bottom-placed sides last year - while the other competitive wins Borthwick has overseen have come against the likes of Japan, Chile, Samoa and Fiji, with two higher-profile successes against Argentina at the World Cup.
A new defensive system under Felix Jones - who worked as a skills coach with South Africa - failed in its task at Murrayfield, while a stated ambition to change England's attack to a more attractive brand has failed to bear fruit yet.
Indeed, outside of the opening few minutes in Edinburgh, England's attack has looked as stunted and limited as it did last year.
Plenty of work to do then, and Six Nations leaders Ireland come to town next. If England play as they intend to, with the talent they have, they are more than capable of shocking Ireland. But if Borthwick's side are off it, Ireland could destroy them.
Scotland firmly in Six Nations title hunt
How much will Scotland end up ruing that controversial last-gasp decision vs France at Murrayfield in Round 2?
Having just about hung on to win in Cardiff for the first time in 22 years in Round 1, and now beaten England for a fourth time in succession in Round 3, if Gregor Townsend's side travel and win in Rome in Round 4 as most expect them to, then but for a brutally tight TMO call going against them vs Les Bleus, they would have been on for a Grand Slam themselves going to Dublin on the final Saturday.
They are still likely to head to Round 5 with just the one loss, and so even if Ireland do beat England, Scotland will most likely be heading to the Irish capital with a chance to win the tournament.
Scotland's last championship success was in 1999, before Italy even joined the tournament, while their last Grand Slam came in 1990.
It's pretty inarguable at this stage that this is the best Scotland side since that 1999 one, and they are firmly in the title mix. For most, they should be on for a Grand Slam.
Ireland's record-breaking form - can they achieve what no one has before?
Ireland's 31-7 win over Wales on Saturday was a record-extending 18th success in a row at the Aviva Stadium, and a record-equalling 11th successive Six Nations Test win (level with England 2015-2017).
The reigning Grand Slam winners have been in form the like of which has rarely been seen in the northern hemisphere before.
Between July 2022 and October 2023 Ireland embarked on a world record-equalling 17-Test winning run, and though they suffered a hugely disappointing World Cup quarter-final loss to New Zealand and saw talisman Johnny Sexton retire, their response has been sensational.
Jack Crowley has come in to start at out-half and thrived, while more new blood in Calvin Nash and Joe McCarthy has added superbly to a group of massively-talented, experienced players.
A trip to Twickenham and Scotland in Dublin will not be easy, but Ireland are now seeking something nobody has achieved in the Six Nations era: repeat Grand Slams. And it's hard to look past them clinching it.
Townsend wary of trusting mouthguard technology that 'hasn't been proven'
Scotland head coach Townsend expressed concerns about the implementation of smart mouthguards after temporarily losing a second player in successive Six Nations matches for a head injury assessment triggered by the new technology.
Asked after the England game if Zander Fagerson's departure from the field was triggered by his mouthguard, Townsend said: "Yes, it was and I saw the tackle again, just a normal tackle.
"I think we have to really watch what we're doing here by trusting technology that's not been proven.
"Zander was taken off for 10 minutes after what looked like a normal tackle but there was a spike alert from the mouthguard.
"I know in Super Rugby there were a couple of alerts and players were saying 'there's nothing wrong here, I've just made a tackle', so we've got to watch that because you don't want to be taking our best players off the field for 10 minutes if there are no issues around concussion.
"We want to protect our players, that's for certain, but there's a bit more work to do before this technology is correct.
"It's a new thing in the Six Nations and it's not been used at club level prior to the Six Nations. I'd hope they'd learn from today's incident, and obviously George Turner went off for 10 minutes in the previous game.
"We need to make sure it's as close to accurate as possible. That's what we want."
Six Nations' remaining fixtures
Saturday March 9 2024
Italy vs Scotland (2.15pm)
England vs Ireland (4.45pm)
Sunday March 10 2024
Wales vs France (3pm)
Saturday March 16 2024
Wales vs Italy (2.15pm)
Ireland vs Scotland (4.45pm)
France vs England (8pm)