Some 70 years since they completed their first clean sweep in the old Five Nations, Ireland will match their 1948 and 2009 predecessors if they see off England on St Patrick's Day, having wrapped up the title with a week to spare.
Officially, only a few thousand tickets in an 82,000 capacity Twickenham have been given to away fans but many more Irish supporters are expected to brave the snow covering much of London and make their way to 'headquarters'.
Deposed Six Nations champions England are reeling from their first back-to-back defeats under coach Eddie Jones following away losses to Scotland and France.
Another reverse could see England, who have not lost a Six Nations match at Twickenham since 2012, finish the Championship in a lowly fifth place.
Yet victory would see England leapfrog Ireland back into second position in the global rankings behind world champions New Zealand.
"It isn't going to take just an ordinary performance and England certainly are not just going to hand us a victory," said Ireland captain and hooker Rory Best.
Meanwhile England captain Dylan Hartley, back at hooker after missing last week's 22-16 loss to France with a calf injury, insisted: "We are still a good team. Two losses don't mean we are not a good team."
Ireland have now won three Six Nations titles in five years under methodical Kiwi coach Joe Schmidt and they are on a national record of 11 successive Test wins – a sequence that started when they denied England a grand slam in Dublin last year.
By contrast, Jones has made 10 changes – seven in personnel and three positional switches – to the side beaten by France in the biggest shake-up of his England reign.
There are new pairings at half-back – regular centre Owen Farrell, the son of Ireland defence coach Andy Farrell, starts at fly-half in place of the dropped George Ford – and also in midfield, while all three rows of the pack have been altered.
Some coaches would baulk from making that many changes at once – but not Jones.
"I love it. This is what we get paid for as coaches," he said.
"It's the best time in rugby, when you are under the pump and you have got to produce it."
The outspoken Australian found himself having to apologise after a video of a speech he gave to corporate sponsors last year in which he referred to the "scummy Irish" and called Wales a "little shit place" surfaced on Wednesday.
Best said he was sure Jones "did not mean to be offensive" while Wales skipper Alun Wyn Jones brushed aside a "poor choice of words" from "Uncle Eddie".
Whichever side wins the match between Wales and France in Cardiff will likely finish second.
A runners-up' spot would be particularly creditable for France, unlucky to be beaten by both Ireland and Scotland in their first two games under new coach Jacques Brunel.
Mathieu Bastareaud will captain France for the first time in the absence of the injured Guilhem Guirado.
"I'm not going to overplay my role. If I feel I have to speak, I'll speak," said the powerhouse centre.
Saturday's action begins in Italy with the Azzurri trying to end a 16-game losing streak in the Six Nations against a Scotland side beaten in 17 of their last 19 tournament away games, apart from wins in Rome in 2014 and 2016.
"Our future is now. On Saturday we want to win against Scotland," said Italy coach Conor O'Shea.
A win for Scotland would see them finish third and might even propel them to second if other results go their way.
"Playing Italy will be a very tough game," said Gregor Townsend, the Dark Blues' boss. "It always has been for any Scotland side."