Last weekend's round of Six Nations games perfectly illustrated the potential of the British Lions to turn up in New Zealand, and be either brilliant or hopeless.
They straddle such a fine line between exploding into life and playing a lethal brand of rugby in New Zealand, or imploding, as they fail to leave behind old scores, national grudges and long-held contempt for one another.
How good they could be was best seen at Twickenham, where England clicked into top gear and played what can only be described as their version of shock-and-awe rugby.
At the heart of their performance was extreme physicality, but it wasn't like the old England of previous decades, where that muscularity was suffocating and pedestrian.
This was different. This was highly conditioned, big athletes playing at pace and with dynamism.
This was England fulfilling everyone else's long-held fear that they would be such a good side, if they could inject agility, mobility and pace into their forward pack.
Players such as Maro Itoje and Courtney Lawes typify England's new direction. These two have work ethic and hunger to sit alongside their natural athleticism, and it's almost freaky that they can both interchange between lock and blindside with such ease.
The All Blacks would love two athletes - two players - of their respective calibre, but the show doesn't stop there. England are using their forwards to create and then exploit space, which is another new trick they have learned under coach Eddie Jones
With that, they have given the likes of Johnathan Joseph and Elliot Daly the platform to show they are class acts.
Lions coach Warren Gatland isn't going to have any problem finding 37 quality players - men who can play at pace, with enough crunch and creativity to be serious contenders to win the test series.
England will no doubt provide the bulk of the squad, but Ireland, Scotland and Wales will all contribute players, and on paper at least, the squad of 2017 will stand comparison with the great Lions team of 1971.
But here's the rub. Can Gatland meld his squad into a cohesive, unified group who can put the team ahead of their personal ambitions?
Can he persuade all those he takes to forgive any slights - real or imagined - that may have occurred during the Six Nations and turn long-term enemies into friends in the space of just a few weeks?
The enormity of that task shouldn't be underestimated. Serving as evidence of how hard that is going to be is exhibit A - the weekend sledge delivered by Wales first-five Dan Biggar to Irish opposite Johnny Sexton.
The latter was yellow-carded for killing the ball on his own line and as the card was brandished, Biggar sought him out and said: "Cheers, Johnny boy ... have a good day, son".
Hardly malicious or off the scale, but indicative nonetheless of the edge between Ireland and Wales. These two have developed a healthy dislike of one another, a point confirmed by Gatland himself last year in his capacity as Wales coach.
"Probably, out of all the teams in the Six Nations, the Welsh players dislike the Irish the most," he said. "Players' experiences against Ireland haven't always been the greatest, so they are very motivated."
The Scots and English have a similarly poor relationship that has festered for years, and there is a danger that the Lions bring the greatest squad in their history, only for it to be disastrously riven with factions and ill-feeling.
Finding harmony and common purpose is going to be harder for the Lions than finding a winning gameplan. Keeping personal relationships positive and driven towards the bigger goal of winning the series is going to be harder than picking the right starting team.
The Lions are going to be compelling, but the question for Gatland is whether the fascination will be with their excellence or dysfunction.