The four Home Union sides are in rude health going into the most open World Cup in the event's history. All four should reach the quarter-finals, although Ireland and Scotland will face a Herculean task against the All Blacks and Springboks.
England are in good shape. Eddie Jones now knows his strongest 15 and has tactical options which will change how they play but will not reduce the side's strength.
The lineout and kicking games have seen significant improvements recently, and both are now formidably good. That means England can really pressure opponents and play for territory, while their possession-based game is also outstanding, with their big men carrying so effectively that they almost always cross the gain line, while operating opensides Tom Curry and Sam Underhill in tandem ensures quick recycling.
That means England are playing on the front foot, and can choose whether to attack the nine-10 channel or move three channels out.
Defensively, England look aggressive and strong. In attack they are patient and able to control games.
I wonder, however, how they will react if Plan A does not work, as happened in the second half against Scotland. Decision-making and tactical adaptation in adversity will be key. Thankfully they have games against Tonga and USA to ease themselves in.
England have two vulnerabilities: a lack of patience and an over-reliance on key players. People cite Billy Vunipola as 'The Man', but the player they cannot lose is Manu Tuilagi. I see England topping their group, then beating Australia in the quarter-final.
Ireland's warm-up Tests were baffling. They were well off the pace against England, but their wins against Wales showed that if they can control the breakdown they can beat anyone. If they don't, their game plan disintegrates and they struggle badly.
I suspect they will play the shrewd Peter O'Mahony at No 8, with C J Stander at flanker, Josh van der Flier at seven, with Iain Henderson an option when extra grunt is required. It is a well-balanced back row, but I fear they will rue leaving Devin Toner behind. When they beat the All Blacks in Chicago he dominated Irish and Kiwi lineouts, which is crucial when you kick to the sidelines so often.
Ireland have good choices everywhere, great experience and a parsimonious defence, all crucial World Cup attributes. They also have, in lock James Ryan, the beating heart of the team; it is difficult to overstate how important he is to them.
Ireland's Achilles' heel is their reliance on Conor Murray and Johnny Sexton. At 30 and 34 respectively, both are getting on and their replacements lack their big-game experience. This is particularly true of Sexton, so it is imperative that Joey Carbery - who has so much to offer - is fit and match-ready.
If Joe Schmidt's side have a surprise package, it is centre Bundee Aki, who excelled against Wales, providing bite in defence and go-forward in attack.
Ireland would not have wanted Scotland first up, but notwithstanding their tendency to bomb at World Cups, they should top the group but go out in the quarters.
Wales could be genuine contenders. If they can beat Australia, which I believe they will, they should face France or Argentina in the quarters, two teams they would expect to beat. Once you're in the semis ...
The way they lost in Dublin, especially the second 40, was very disappointing, but they have strength in depth, lots of options, tons of experience and more proven big-game winners than any other Six Nations side. Chief among those is Alun Wyn Jones, whose captaincy has a huge impact upon the team he leads, as does the peerless Jonathan Davies's leadership in midfield.
Wales are more than the sum of their parts, which shows in both defence and attack. In defence, they are aggressive and possibly better organised than any other side in world rugby. That is thanks to defensive genius Shaun Edwards, but also to their patience.
This is an organised side who are happy to defend through 15 or 20 phases and never lose their shape.
The same is true in attack, where their reservoirs of patience seem never-ending. The Welsh players' profound confidence in their systems explains why they won the Six Nations.
If they have a weakness, it's that - the Paris comeback notwithstanding - they are not set up to chase games.
Their style is all about exerting pressure by dominating territory and/or possession, so despite the presence of brilliant attack-minded players like Liam Williams, if they go 15 or 20 points behind then they struggle.
Scotland face an uphill struggle against Ireland, should overwhelm Samoa (although they only beat them by three points in 2015) and will hope they can repeat their hard-fought 2-0 series win in Japan from 2016 when they play their last pool game. I see Scotland losing in the quarter-final.
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