In the finest tradition of the tournament, the destination of the title will go to the last match - France against Ireland in Paris. Given the championship's penchant for keeping everyone in suspense, who knows it could still be in the balance until the final moments of the final match.
Logic, a word difficult to find in the RBS 6 Nations' vocabulary, dictates that the 2014 silverware is Ireland's to win, or lose. Victory by the narrowest margin at the Stade de France will surely make them champions and send their most venerable player into contented retirement.
While Brian O'Driscoll won't necessarily see it as being that clear cut, Ireland for once are in control of their own destiny. The superiority of their points-difference is such that even in the unlikely event of England winning by 50 clear points in Rome, a one-point Irish win would be enough to take the title.
Since their admission to the Championship, Italy have lost by 50 or more just once, at Twickenham in 2001 (80-23) to exceptional opponents then on their way to winning the World Cup. The same England team had by then topped 50 at the Stadio Flaminio but even they had to settle for a winning margin three points shy of half a century.
O'Driscoll, of course, has been that way before in the very same part of the Eternal City, on the last weekend seven years ago. Ireland, ironically, did top 50 as the occasion demanded, not so much because it happened to be St Patrick's Day but because France went into the last round holding a fragile advantage on points-difference, +69 against +65.
Under O'Driscoll's captaincy, Ireland responded well enough to leave France with everything to do later that same afternoon, Scotland in Paris. The Irish could hardly have done more in Rome what with eight tries even if they were undone going for a ninth in the last minute.
Nobody will ever know for certain but the title would surely have been theirs had their last attack not broken down and paved the way for an Italian try instead, finished off by Roland de Marigny, a South African from Durban. In what would prove, ironically, to be his last act in the Test arena, Andrea Scanavacca landed the conversion.
The French victory target had been lowered from a highly improbable 31 points to 24. Having gone 25 clear after 62 minutes, Les Bleus under Raphael Ibanez were cruising until the Scottish prop Euan Murray scored a try four minutes from time which promised that perhaps the title would be Dublin-bound after all.
By then the Irish squad were back at their Roman hotel, joining those crowded around a television in the lobby. Chris Paterson's attempted conversion from the touchline rebounded off a post and it wasn't until deep into stoppage time that France restored the decisive margin with a try from Elvis Vermeulen.
Even then, the entire French and Irish nations, or so it seemed, had to wait even longer for the TMO to confirm that the substitute back row forward had scored. Once the anguish had subsided, Ireland knew they had lost the title a few weeks earlier back at Croke Park where Vincent Clerc's late try cost them a Grand Slam.
England know all about that ever-hazardous business. Their stylish disposal of Wales at Twickenham brought their young team the reward of a Triple Crown even though they had loftier goals in mind when the tournament began last month.
Had they not been undone by the capricious bounce of the ball on the opening weekend in Paris, England's best team since 2003 would have been back where they finished up last year, playing for the Slam.
Had they eliminated Wales from the title race last Sunday by at least 20 clear points, it would have been no more than their impressive young side deserved.
Strangely given a three-quarter line of Test Lions, the ex-champions have lost their way without a single try to show for their two away matches.
While they finish up at home to Scotland playing for third place, at best, the more important issues will be settled on the continent. History tells us not to be surprised by anything that happens between the last fence and the finishing post.
Take the last match of the Five Nations as a classic example. It provided a climax that will be talked about forever by those who witnessed it - Wales against England at Wembley under a cloudless sky on Sunday, April 11, 1999.
With Cardiff Arms Park in the final stages of its conversion into the Millennium Stadium, Wales relocated to the home of English football when it still had the famous twin towers. England, unstoppable in the three previous matches, went there as odds-on favourites to win an away match in their own capital. How convenient.
As the final minutes ticked by, a tournament official took the trophy out of its wooden box and began festooning it with white ribbons. Seconds later, Scott Gibbs set off on his side-stepping run for his famous try and by the time Neil Jenkins won it for Wales with his conversion, the trophy had been put back in its box, to be flown to Edinburgh instead.
Scotland had thrashed France 36-22 the previous day, hardly imagining that they would end up winning the last Five Nations on points-difference.
England lost two more Slams over the next two seasons, at Murrayfield in 2000 and Lansdowne Road in 2001 when the food-and-mouth epidemic forced the match to be postponed until the October of that year. On each occasion, they won the title, not that it felt much of a consolation at the time.
Ireland, beaten by Martin Johnson's England in the double Grand Slam finale at Lansdowne Road in 2003, were last involved in a points-difference decider in 2006. A French victory in Cardiff two hours earlier sent Ireland into the last match of 'Super Saturday' facing the tallest of orders at Twickenham - beating England by 34 points.
They beat them by four instead, enough to finish runners-up. O'Driscoll, of course, experienced that scenario and just about every other over the course of a monumental career which first took him to Paris during the inaugural Six Nations championship 14 years ago.
He marked the occasion with a hat-trick of tries and has scored more against France in the Championship than anyone else - six in eleven matches.
Head coach Joe Schmidt has given Ireland, among other things, real conviction. According to fly half Jonny Sexton, Ireland have 'the best coach around...a game-plan everyone trusts' and they will settle for nothing less than 'finishing the job.'
Schmidt leaves nothing to chance, not least the subject of 'mind fitness.' Responsibility for that lies with Enda McNulty, a sports psychologist and former Armagh GAA footballer who won an all-Ireland medal with his native county in 2002.
If the arithmetic works out in Ireland's favour, neutrals the world over will be treated to the storybook finish, of the world's most-capped player riding off into the sunset with a trophy decorated in ribbons of emerald green.
Should that come to pass, Stuart Lancaster's rising England squad will not be slow to send their congratulations. With Mike Brown, the No. 1 contender for Player of the Tournament, as their last line of defence and often first point of attack, England will aim to finish off in style.
And then they can only hope to watch France finish the way they started at England's expense, with a home win. In that event, Chris Robshaw will be collecting a bigger trophy than the Triple Crown as due reward for having won the match of the championship against Ireland at Twickenham last month.
Only Rugby's Greatest Championship could stage-manage such an intriguing climax. Ireland may have managed just one win in France in more than four decades but form and self-belief all point to the St Patrick's Day celebrations kicking off in Paris on Saturday night.
My team of Round 4:
15 Mike Brown (England)
14 Yoann Huget (France)
13 Brian O'Driscoll (Ireland)
12 Billy Twelvetrees (England)
11 Leonardo Sarto (Italy)
10 Jonny Sexton (Ireland)
9 Danny Care (England)
1 Cian Healy (Ireland)
2 Rory Best (Ireland)
3 David Wilson (England)
4 Joe Launchbury (England)
5 Courtney Lawes (England)
6 Iain Henderson (Ireland)
7 Chris Robshaw (England)
8 Ben Morgan (England).