That was much more than a reality check. The mystique which takes time to build was smashed in Dublin and Ireland won with something to spare.
Despite the close-looking 13-9 scoreline, any other result would have been a travesty, with the England pack given a torrid evening.
I was surprised by the superiority Ireland showed in so many aspects, despite going into the game without key players Conor Murray and Rob Kearney and losing Jamie Heaslip in the warm-up.
Make no mistake, Saturday was a significant loss for England against a team who are not going to go away.
Ireland will keep improving; they have a strong Under 20 set-up and a world-class coach in Joe Schmidt who goes about his job in a very different way to Eddie Jones.
It should be added that Andy Farrell did a magnificent job organising the Ireland defence which never looked like leaking a try.
There is still a debate about the influence of 'rugby league' coaches but in Dublin we saw the very best of what they have to offer. Hopefully he can work the same trick for the Lions in New Zealand but he is proving a significant signing by Schmidt.
England were well beaten and bear in mind that they could easily have lost to France and Wales, too. They did very well to quarry out two wins there but the truth is that the champions might easily have finished third or fourth.
The bubble has finally burst. The world record-equalling run is over and that is probably no bad thing because there is much work to do, as most people appreciated. Certainly Eddie has never stopped stressing that.
After two Six Nations and a three-Test series in Australia, Eddie is at the end of Phase One with this England team and 18 wins out of 19 is a record nobody would have envisaged when he took over amidst the rubble of the 2015 World Cup campaign. He has done a really excellent job but Saturday will have shocked him - not losing but the manner of the loss.
Now sees the start of Phase Two, starting with the summer tour to Argentina with a squad that will be shorn of Lions.
That will take England up to the summer of 2019 when they must start specifically preparing for the World Cup in Japan. It will be a very different team trying to win a World Cup than the one dismantled by Ireland.
Eddie and the players have put England in an excellent position, restoring pride and respect, but this defeat will take some getting over, especially given the disruption the Lions tour will bring.
In Phase Two everybody selected must potentially be a World Cup starter. Selection must be more ruthless than ever.
If they are going to be too old, not quite good enough or cannot be trusted to have the fitness to go head to head with the All Blacks for 80 minutes, then a parting of the ways must come now - if World Cup success is to be achieved.
Ditto if their skillset doesn't fit the requirements of the modern game or if their faces simply don't fit with the coach.
Can Dylan Hartley - a revelation and a complete success as the team's captain - continue as first-choice hooker? How much longer will Dan Cole go on for?
Will there be room for James Haskell and a fit-again Chris Robshaw - superb England servants both - in an England back row that badly needs an injection of real pace at No 6 and No 7? And where are those back-row players blessed with pace?
Do they fast-track England Under 20 captain Zach Mercer? How should Maro Itoje be deployed? What is Elliot Daly's best position?
Is there any room for the exceptional talents of Christian Wade or Danny Cipriani or is it curtains for them? How do England utilise the skill of Henry Slade, who rarely gets mentioned these days? Will Mike Brown be full-back right through to 2019?
England's forwards can overpower some packs - such as Scotland - but against the very best they still look a yard slow from No 1 through to No 8 and that must be improved over the next two years.
Ireland, Wales and France showed them up badly in that respect.
I can guarantee Steve Hansen and his New Zealand coaches will have looked at the England pack and licked their lips at the prospect, when the two teams finally meet, of moving them around the paddock at high speed for 80 minutes.
The good news is that apart from the mysterious lack of a natural No 7, England have a huge player base and all sorts of options to utilise as they move up to the next level from this great launching pad.
This is an exciting time for English rugby.