Opportunities such as the one England face in France on Saturday do not come around often.
Not just because it is a Grand Slam decider. Not because of the sell-out partisan crowd. Not even because France will be their World Cup pool opponents in five months' time.
But because for the first time since July 2019, England might lose. The jeopardy that comes with that presents a golden opportunity not only for them, but for the entirety of women's rugby.
The professional Red Roses have snaked a trail of destruction through the 2022 Women's Six Nations as they seek a fourth successive title and now a 23rd win in a row.
Victory has never been in doubt as they have scored 42 tries and conceded just two, with winning margins of 50 points or more in all four of their matches.
France have also secured four bonus-point wins and on Saturday, both sides will finally get a chance to truly test themselves.
As women's rugby basks in the glow provided by its new window away from the men's event, the winner-takes-all game is the chance to go to the next level.
France have often led the way in promoting their women's side and near the stadium in Bayonne, taxi drivers merrily discuss their side's chances, while the local radio station pauses between songs to remind people to tune into the match.
The hype and the competition are so high that England head coach Simon Middleton feels the learnings for October's World Cup are as much of a reward as the Grand Slam at stake.
"It will be a benchmark of where we're at and that's probably as important in the context of this year as any outcome," he said.
'The most brilliantly brutal atmosphere'
Throughout the 2022 Women's Six Nations, England have had to find motivation from within as they have breezed past their partly professional or amateur opponents.
On Saturday, there will be a loud external impetus they cannot ignore.
The game in Bayonne has been sold out for more than a month with a French rugby public, whipped into a frenzy by the men's Grand Slam six weeks ago, eager to see if the women's side can follow suit.
England are accustomed to large crowds after setting two record attendances in a row at their home games during this tournament.
But rather than rousing the crowd of 10,600 with their exciting attack as they did then, Middleton says the plan this time is "to shut everybody up".
England lock Abbie Ward agrees she will find motivation in "the most brilliantly brutal atmosphere you will ever be involved in".
"You know if they've got thousands of fans there, maybe 100 will be with England, so there are thousands waiting to see you slip up - I thrive on that," she continues.
"It doesn't get much bigger than France away so we're all incredibly excited to be a part of it."
'Winners will be world champions'
As if the stakes were not already high enough, former France international Laura di Muzio says "the team that wins on Saturday will be world champion" come October's showpiece in New Zealand.
A rather large obstacle stands in England's way: the formidable French pack.
Les Bleues' forwards were almost the Red Roses' undoing in 2021's one-off Six Nations final and they have the best scrum success rate in the tournament this year, besting England by 97% to 92%.
The Red Roses' recruitment of forwards coach Louis Deacon had an immediate impact in two record wins against New Zealand last autumn.
They will hope for more of the same in what is likely to be an attritional affair as the two best defences in the tournament go head to head.
England have lost captain Sarah Hunter to a rib injury but there is no shortage of star players in the pack.
Poppy Cleall steps in at number eight, with prop Sarah Bern and flanker Marlie Packer starring throughout the tournament and world player of the year Zoe Aldcroft recently returning to fitness.
Prop Vickii Cornborough believes they have done enough to turn things around up front.
"We want our scrum to be a weapon and it's something over this past year we've been focusing on," she told BBC Radio 5 Live's Rugby Union Weekly.
'France could be sleeping giants'
On paper, the statistics do not seem to be in France's favour for the 50th Test between the sides.
England are fighting for a 10th straight win against their cross-channel rivals and while the Red Roses have run away with games in the final quarter this year, France have stalled late on.
Despite also beating New Zealand in the autumn, Les Bleues' grip on the world game is not as tight as England's.
Should they lose on Saturday, they will cede third place in the world rankings to Canada and drop to fourth.
But the hosts are buoyed by the return of fly-half Caroline Drouin - pushing the tournament's leading points scorer Jessy Tremouliere to the bench - while star scrum-half Laure Sansus leads the try-scoring table with six.
The passionate home crowd and lure of a Grand Slam could be just what they need to wake from their slumber.
"We've seen their ridiculous superstars doing their thing every now and again," former Wales international Philippa Tuttiett says.
"I just don't think we've seen the best of them. I really think France could be sleeping giants."
England: Rowland; Thompson, Scarratt (capt), Aitchison, Breach; Harrison, Infante; Cornborough, Davies, Bern, Aldcroft, Ward, Matthews, Packer, Cleall.
Replacements: Cokayne, Botterman, Muir, Galligan, Beckett, Kabeya, Hunt, Kildunne.
France: Jacquet; Boujard, Filopon, Vernier, M Menager; Drouin, Sansus; Deshayes, Sochat, Joyeux, Fall, Forlani, Ferer, Hermet (capt), R Menager.
Replacements: Touye, Lindelhauf, Brosseau, Annery, Gros, Chambon, Tremouliere, Boulard.