It has been the subject of fevered debate in northern hemisphere rugby for months, providing a subtext to the recent Six Nations and occupying the thoughts of every elite player across Britain and Ireland.
Who will make the Lions squad for the tour of New Zealand?
The time for speculation is almost over.
On Tuesday, Warren Gatland was meeting with his backroom staff to finalize an expected 37-man squad — a mix of English, Irish, Welsh and Scottish players — tasked with the toughest assignment in rugby: Going from rivals to comrades in the space of a month and gelling to defeat the world's best team.
The squad for the 10-match tour, which culminates in a three-test series, is announced in London on Wednesday.
The Lions have won just one series in 11 trips to New Zealand, 2-1 in 1971, and were demolished 3-0 on their last visit in 2005 by a rampant All Blacks side led by the imperious Dan Carter.
No wonder the New Zealand-born Gatland has called it the "ultimate test."
Since being appointed as Lions coach for the second straight tour, Gatland has taken a sabbatical from his regular job in charge of Wales to plot the downfall of the world champions. He has visited New Zealand, scoured the domestic and European club scene, and cast a keen eye on the Six Nations won by England over February-March.
European rugby is in a healthy state, with northern hemisphere teams winning nine tests against southern hemisphere beasts New Zealand, Australia, South Africa, and Argentina during the November internationals. There will be a lot of top-quality players left out by Gatland, sparking uproar throughout the home unions.
Here are some of the talking points ahead of the highly anticipated squad announcement:
Three names have been in the frame: Sam Warburton, Alun Wyn Jones (both Wales) and Rory Best (Ireland). Warburton, though, is the favorite.
The 28-year-old flanker was captain for the 2013 tour of Australia, and led Wales under Gatland from 2011 until standing down ahead of the Six Nations to regain his form.
Warburton has a score to settle after missing the series-clinching win in the third test against Australia four years ago because of injury.
A knee ligament injury while playing for Cardiff Blues on April 7 has ruled him out for about six weeks, meaning he will not have much time to prove his match fitness ahead of the Lions' tour opener on June 3 against the New Zealand Provincial Barbarians in Whangarei.
He might not like the label but Gatland is known for his so-called "Warrenball" approach: In crude terms, sending his big men into collisions on the gain line, phase after phase, to gradually gain yardage and eventually create openings in a tiring defense.
It has brought Gatland and the Welsh plenty of success on the domestic front — including two Grand Slams in the Six Nations — but has never led to a victory against New Zealand. He also has a poor record against the other southern hemisphere giants.
Nevertheless, he is expected to go that route again with the Lions. That means loading up with tough, uncompromising players in the forwards, strong runners in midfield, and putting together a powerful scrum.
With ferocity set to trump finesse, it has been reported in the British media that Joe Launchbury — a star for England in the past two years — could miss out in the face of intense competition in the second row, and that compatriot Jonathan Joseph, a silky runner in the Jeremy Guscott mold, could also be overlooked.
England is likely to have the biggest contingent in the squad, having just embarked on a tier one-record-equaling run of 18 straight test wins. However, the streak ended with a 13-9 loss to Ireland on the final weekend of the Six Nations and that Grand Slam-denying result could have consequences.
As well as Launchbury and Joseph, past and present captains Dylan Hartley and Chris Robshaw may also miss out, as might fullback Mike Brown and flyhalf George Ford amid fierce competition.
It revives memories of 2013, when the English had fewer Lions tourists than expected on the back of a 30-3 loss to Wales in Cardiff that cost them the Six Nations title and a Grand Slam.
The Scots have just finished third in the Six Nations, for their most successful tournament since 2006, and exhibited an attacking intent not seen in years. They are set for disappointment on Wednesday, though.
Fullback Stuart Hogg appears to be Scotland's only guaranteed tourist, especially with tighthead prop WP Nel out injured. The country's quota is set to be way down compared to the Welsh, who were fifth in the Six Nations.
There are usually one or two picks from leftfield for Lions tours. They might be hunches. Some may get selected because they are viewed as potentially good tourists.
This time, prop Kyle Sinckler (no test starts, eight substitute appearances for England) could benefit, as could New Zealand-born England center Ben Te'o (eight caps).