Sam Warburton caused a mini-storm last month when he claimed Ireland are the best men’s rugby team in the world. South Africa fans, never knowingly lacking in passion when it comes to any matter relating to Springbok rugby, jumped all over the ex-Wales flanker. They, not unfairly, pointed towards the World Cup that the Boks won for the second consecutive time last autumn, in a tournament where Ireland (again) exited at the quarter-final stage.

Fast forward a few weeks and so brutal has the destruction and havoc been that Andy Farrell’s men have wreaked on every opponent during this Six Nations that when Steve Borthwick emphatically declared the same ahead of his England side welcoming the all-conquering men in green to Twickenham this weekend, barely an eyebrow was raised. “Let’s be clear on Ireland right now,” stated Borthwick at his pre-match press conference. “We can all agree they’re the best team in the world. They might not have won the World Cup but, right now, the way they’re playing, the way they’ve been playing through the first period of this championship, they are the best team in the world.”

Perhaps that is unfair on South Africa, who haven’t played a match since beating New Zealand 12-11 in the final of a competition literally designed to decide the best team in the world yet have to put up with the rugby intelligentsia declaring they’ve been surpassed, but Borthwick and Warburton’s wider point stands. Ireland are currently untouchable, at least in a Six Nations context.

When England examine their opponents’ team sheet ahead of Saturday afternoon, it’s almost impossible to find a hole. A front row of Andrew Porter, four-try Dan Sheehan and Tadhg Furlong have dominated at scrum-time and Joe McCarthy has slotted so seamlessly into the second row alongside Tadhg Beirne that captaincy candidate James Ryan was merely a bench-warmer even before his tournament-ending bicep injury. Meanwhile, the trio of Peter O’Mahony, Josh van der Flier and Caelan Doris have every facet of modern back-row play covered from jackal threat and relentless defence to barrelling ball-carrying and on-field s***housery.

Jamison Gibson-Park is comfortably the best scrum half in the northern hemisphere when players who are not from this planet are excluded, Hugo Keenan doesn’t even require that caveat when discussing full backs, Bundee Aki’s remarkable late-career renaissance has formed a centre partnership with Robbie Henshaw so solid that a fit-again Garry Ringrose will be forced to watch the Twickenham clash on TV, James Lowe should probably be under investigation for having a cannon masquerading as a left boot and Calvin Nash’s superb performances may have Mack Hansen regretting his decision to have Farrell’s face tattooed on his leg, given that the Ireland coach might now never call him again.

The physicality of their attack is breathtaking, as shown by four of the top five players for metres made in contact during this Six Nations being Irish (Doris, Lowe, Nash and Aki joining England’s Ben Earl) but it’s also ruthlessly efficient. Ireland are averaging the most 22 entries per game in this year’s championship (10) but also averaging the most points per 22 entry (3.4). No one reaches the 22 more than Farrell’s men and they’re leaving with more than a penalty every time – no wonder 21 points is their smallest margin of victory so far this year.

Perhaps the only minor question left to answer for Ireland comes at No 10. This is not to diminish what Jack Crowley has done by stepping into Johnny Sexton’s shoes. There were genuine concerns ahead of the tournament that Sexton was irreplaceable in the Irish system and as their emotional leader but Crowley has directed the attack to impeccable results, as detailed above, while fellow Munsterman O’Mahony has been an equally inspirational, tone-setting captain. The fact that Sexton’s name stopped appearing in articles about Ireland pretty much as soon as round one was finished is testament to both men.

But there’s a nagging feeling that Crowley has not been truly tested yet and that as long as Ireland’s attack is humming along in cruise control, he hasn’t proven he can overcome adversity at Test level. This, of course, is not his fault – after all, it’s unfair to hold someone responsible for playing in a team that’s too good – but if England are to spring an almighty Twickenham surprise, then the route to victory probably runs through disrupting Crowley.

“I think it’s a big game for Jack Crowley,” said Ireland legend Brian O’Driscoll onOff The Ball this week. “He did pretty well against a disappointing France team and recovered well. It’s been easy going against Italy and pretty easy going against Wales albeit they put it to us in the second half. This is a massive game for him. Can he find the right holes, can he pick the right passes and can he play a similar game that he’s played in those first three matches and be the facilitator to bring out the best in the other players?”

Much has been made of the new, aggressive blitz defence system that England coach Felix Jones has been implementing since joining the set-up from the Springboks after the World Cup and, while it’s still a work in progress, there have been promising early signs. It spooked inexperienced Wales fly half Ioan Lloyd in the round two victory and disrupted Italy in Rome, especially in the second half. Even Finn Russell took a little while to figure it out a fortnight ago before ultimately orchestrating Scotland’s attack, with no little help from a rampaging Duhan van der Merwe, to 30 points in a Calcutta Cup victory. Eighty-odd caps of international experience at fly half will help with that.

Crowley will have defenders in his face within a split second of receiving the ball. He will have to read the defence, find the crack to exploit and execute his skills quicker than he has ever done in his rugby career so far. This will be a test of Crowley’s brain rather than his brawn. Can he compute and analyse with 115kg of flying Maro Itoje coming at him? If he can, the gaps will open up and the rewards are huge. But if he can’t...

“Ireland’s attack wants to put people under an awful lot of pressure,” explained Borthwick. “So we’re going to be really tested there. And I’m looking forward to seeing our defence under this test. What we’ve been able to do is force teams to change the way they’re playing a little bit. We’ve forced teams to make a number of errors. Now quite clearly playing against Ireland, if they’re allowed to get into their rhythm, then they’re a very strong side. So we need to ensure they don’t get in that rhythm.”

England’s attack has struggled so much and Ireland’s defence is so impenetrable under the tutelage of Simon Easterby that it may not matter even if Crowley does fail. It’s hard to see the hosts scoring enough points to defeat the green machine as their inexorable march to the grand slam appears set to go on.

But Ireland may just get an answer to one of their few remaining questions at Twickenham on Saturday. Jack Crowley has been exceptional so far but faces his biggest test yet – can he deliver under pressure? If he can, that ‘best team in the world’ claim becomes just a little stronger.