A win over New Zealand comes along as rarely as a missed tackle by Richie McCaw.
Two victories in a row over the world's most dominant team? Surely no chance.
Yet, that's what England are aiming to achieve on Saturday in the most eagerly anticipated match of the autumn rugby series.
The All Blacks have been forced to wait almost 12 months for a chance to avenge their 38-21 loss to the English at Twickenham last December - their only defeat since August 2011 and their only slip-up since Steve Hansen took charge after the country's World Cup win that year.
"We are playing against the best team in the world, probably the most successful team in world sport," said England coach Stuart Lancaster. "They will have huge motivation to beat us after last year but you have to believe you can win going into any game and this one is no exception."
The scarcely believable scenes from last year's match already armed the All Blacks with plenty of motivation, but they have something else to stick up on the blackboard before the game.
When asked this week if New Zealand's pack was there for the taking, England forwards coach Graham Rowntree said: "Yes, we believe so."
Confident words from a coach whose team have blown hot and cold so far this autumn, using a strong second half to come from behind to beat Australia 20-13 and then a brilliant first-half performance to set up a 31-12 win over Argentina last Saturday.
The other two lots of 40 minutes were distinctly average, and a New Zealand team in form would have put England out of sight in both games.
The All Blacks have won all of their matches this year to strengthen their No 1 ranking, and painful memories of last year will be driving them on.
"I don't want to use revenge," Hansen said. "Revenge is a hurtful word, and rugby is a beautiful game.
"We were completely outplayed by them last year but this is an opportunity for us to see if we have improved our game to the point where we can be competitive ... we know the England coaching staff have done a lot of homework so this may be a game where we add a few new things they haven't seen before."
The tourists will have a massive advantage in experience. Fly half Dan Carter will make his 100th test appearance and joins three other centurions - McCaw, hooker Keven Mealamu and prop Tony Woodcock - in a line-up containing a total of 959 caps.
The All Blacks' starting XV features one change from the line-up which beat France 26-19 in Paris last weekend, with Julian Savea replacing Cory Jane on the left wing. Lock Luke Romano takes the place of flanker Sam Cane on the bench.
England also have one change, bringing back Dan Cole to the front row in place of David Wilson. Fellow prop Matt Mullan was named among the replacements as Alex Corbisiero and Mako Vunipola are injured, while scrum half Ben Youngs is back on the bench in place of Danny Care.
There are still major misgivings about England's midfield, with Joel Tomkins and Billy Twelvetrees given another opportunity to impress after stuttering against Australia and Argentina.
The first-choice centre pairing of Brad Barritt and Manu Tuilagi were in rampaging form against the All Blacks 12 months ago but are out injured and have been sorely missed.