Ireland rugby coach Joe Schmidt insists nothing in his extensive career will have prepared him for the task of trying to guide his adopted country to a Triple Crown away to England in the Six Nations on Saturday.
The New Zealander is in charge of an Irish side currently eyeing a Six Nations Grand Slam after crushing Dublin drubbings of both Scotland (28-6) and defending champions Wales (26-3).
But Ireland will arrive at 'fortress' Twickenham looking for their first win over England in four attempts and with the hosts themselves buoyed by a 20-0 thrashing of Scotland at Murrayfield last time out.
At stake for the Irish is the Triple Crown, the prize one of the four Home Nations - England, Scotland, Ireland and Wales - gets for beating all the others in a single Six Nations season.
Twice a European Cup winner when in charge of Irish province Leinster, Schmidt was under no illusions about the difficulty of trying to steer Ireland to their first victory at Twickenham since 2010.
"There have been some challenges that would stand out in my mind but none as tough as this," said Schmidt.
The coach has been able to name an unchanged side from the team that overpowered Wales thanks to the work of such uncompromising forwards as Ireland captain Paul O'Connell and blindside flanker Peter O'Mahony.
But England, whose pack includes captain Chris Robshaw, Billy Vunipola and Courtney Lawes, are no slouches up front either.
"In physicality, fitness and mental stakes the step up is huge," O'Connell said.
Behind the scrum, Ireland boast several more Lions, including halves Conor Murray and Jonathan Sexton.
But, as has so often been the case, there will be plenty of attention on Brian O'Driscoll.
The Ireland centre, fit following a stomach bug, will equal former Australia halfback George Gregan's world record of 139 caps on Saturday in what will be his final international at Twickenham before he retires at the end of the season.
England coach Stuart Lancaster was equally well aware of O'Driscoll's class but warned against concentrating too much attention on the midfield maestro.
"He's a key cog in the team, but there are other key cogs, the halfbacks are excellent, Paul O'Connell in the second row, (Jamie) Heaslip at No.8, the list goes on of experienced players who make that team tick."
Lancaster has been forced into making a change, with the fit-again David Wilson replacing Dan Cole after his fellow tighthead prop suffered a season-ending neck injury.