Six Nations title scenarios
Twickenham - If Wales beat Ireland in Cardiff on Saturday they will be crowned Six Nations champions, having completed a Grand Slam by triumphing in all five of their matches this tournament.
But if Warren Gatland's men slip up at the Principality Stadium, the destiny of the title will become more complicated.
With England and Ireland still in contention, we look at the possible title scenarios ahead of an intriguing last day in the 2019 Six Nations Championship:
Here is how the table looks heading into Saturday's final round of matches (played, won, drawn, lost, points for, points against, bonus points, total points):
Wales 4 4 0 0 89 58 0 16
England 4 3 0 1 146 63 3 15
Ireland 4 3 0 1 94 75 2 14
Scotland 4 1 0 3 67 87 2 6
France 4 1 0 3 68 104 2 6
Italy 4 0 0 4 65 142 0 0
Points awarded as follows:
* Team that wins the match awarded four match points or, if it scores four tries or more in the process, five points.
* Team that loses the match gets no points or one if it scores four tries or more in the process and two if it both scores four tries and loses by a margin of seven points or fewer.
* Teams that draw a match shall each get two match points and any of them that scores four tries or more in the process shall receive a further one match point.
* A team that wins all five of its matches and so completes the Grand Slam shall be awarded a further three match points.
Final day fixtures, all March 16:
Italy v France, Rome (14:30 SA time)
Wales v Ireland, Cardiff (16:45 SA time)
England v Scotland, Twickenham (19:00 SA time)
Any Welsh win will see them to the Triple Crown (the prize for beating all the other 'home unions' - England, Scotland and Ireland - in a single Championship season), the Grand Slam and the Six Nations title.
Wales and England could both finish on 20 points but any side that completes a Grand Slam gets three extra points.
Wales will finish on at least 23 points if they beat Ireland, putting them out of sight of England.
England will take the title even though England, Wales and Ireland would have all won four matches and lost one. That's because all of England's victories in this Championship have come with a bonus point as they've scored four tries or more against Ireland, France and Italy.
Wales, by contrast, have yet to secure a single bonus point.
Even if Wales were to lose with two bonus points (by scoring at least four tries and losing by seven or fewer points or less) they could only get to 18 points. Any England win takes them to at least 19 points, while a bonus point would give them 20 points.
Even if Ireland beat Wales with a bonus point, they can only get to a maximum of 19 points.
The Irish could end the tournament level with England on 19 points but England's far superior points difference effectively means the title is theirs in this scenario.
The points difference of each side heading into the final day is: England +83, Wales +31. Ireland +19
In this scenario, Ireland would need to beat Wales by more than 64 points than England beat Scotland to take the title on points difference.
If Ireland beat Wales with a bonus point in this case they retain their title on 19 points.
If Ireland win without a bonus point, it takes them to 18 points. England would no longer be in contention because even if they gained two losing bonus points against Scotland, they would only have a maximum of 17.
Wales, however, can lose to Ireland and still reach 18 points if they score at least four tries and lose by fewer than seven points.
In this scenario, a Welsh defeat by five points or fewer would mean they had won the title on points difference.
If Ireland were to win by exactly six points, the teams would be level on points difference but Ireland would win the Championship on tries scored, as long as Wales don't score four more tries than them in defeat.
If the teams finished level on points, points difference and tries scored, the title would be shared.
The three teams at the top could all end on 18 points if this happens should Wales lose but still collect two bonus points, Ireland win without a bonus point and England draw with a bonus point.
England's superior points difference would likely see them to the title.
But England cannot win the Six Nations without a bonus point in a draw with Scotland.
A bonus point win for Ireland wins them the Championship, even if England get a bonus point draw.
England win the Championship in this case. They and Wales might finish level on 19 points but England's points difference would see them to the title.
Bonus points will now be the determining factor. If England draw and score four tries or more in the process, they will likely win the title unless Wales get a bonus point of their own, because of their super points difference.
Wales win the title.