London has already turned German.
There are more than 150,000 followers of Dortmund and Bayern Munich expected to flood into the capital over the weekend and yesterday the advanced party was already moving into place. By tomorrow lunchtime, the city will be awash in luminous yellow shirts and leather shorts.
Not just any leather shorts, either. But official Bayern lederhosen, smart looking traditional Bavarian mountain gear, with a discreet Bayern crest on the leg, as worn by Bastian Schweinsteiger on the club’s merchandise website.
Never mind that, in his modelling role, Basti looks about as comfortable as David Cameron at a UKIP fund-raiser, those items are shifting.
Indeed, what Bayern and – to a lesser extent – Dortmund will be doing at Wembley tomorrow is not only delivering a lesson in football to the watching host nation, but a lesson in how to run a club.
Buoyed by sales of those leather chaps, Bayern are the world leaders in commercialising the game. If you thought Manchester United were coining it with their international marketing deals with Bulgarian telecoms providers and Malaysian potato snack manufacturers, they are as nothing compared with the financial muscle of Bayern.
For a start the Bavarians are debt free; their ownership – in part by the fans – protects them from leveraged buyout. Like every club in the Bundesliga, their constitution ensures there is no chance of takeover by rapacious outside interest.
They have a superb, huge and vibrant home stadium that is always full and where the less well-heeled fan can find a position for no more than 20 euros a match. They have more commercial income than any other club in the world, which they use not to pay down debt or as dividend to a foreign owner, but to invest in infrastructure and personnel.
So much so that in their homeland they have come to be seen as a symbol of avariciousness. So financially muscular have they become, the worry is they will soon detach themselves from the rest of German football.
Already they are threatening to turn the Bundesliga into a monopoly, hoovering up the best talent in the land and as a consequence winning every local trophy available. And that’s before Pep Guardiola even joins as coach.
The fear among followers of other clubs is that Bayern have used the stability and security of the German model of club ownership to propel them into a position of domestic, if not world, domination.
Which is why the entire German nation outside of Bavaria will be rooting for their vibrantly-clad opponents tomorrow.
It would be absurd to cast Dortmund, the eleventh richest football operation in the world, a club backed by the biggest, most lively terrace full of supporters in Europe, as some sort of romantic underdog.
Despite the best efforts of their vivacious manager Jurgen Klopp to present them as a bunch of happy-go-lucky working class heroes somehow finding themselves promoted way above their pay scale, they are a big, booming business.
Never mind the fans’ humorous chant about the Bayern chief executive Uli Hoeness’s current dispute with the German revenue – “stand up, if you pay your tax” - never mind the fact that their wage bill is currently less than that of Queen’s Park Rangers, Dortmund are no impoverished outsiders.
Sure, Bayern may have lured away their best player – the injured Mario Goetze – with barrow loads of filthy lucre, but they have the financial wherewithal to buy any replacement they wish.
Yet, compared to Bayern, with their growing sense of entitlement, there is something refreshingly unpredictable about Klopp and his side. Maybe it is just his magnificent post-match press conferences, more a theatrical turn than a grudging duty, that give the impression that every Dortmund performance is an event.
But then, the way they go about their business on the pitch makes it hard to look away.
After scraping through with the help of a myopic referee and a couple of last gasp goals against Malaga in the Champions League quarter final, they were expected to be blitzed by Madrid in the semi.
Instead it was Jose Mourinho’s team who were at the wrong end of a hammering, the Spanish hegemony at the top of the game torn to shreds by Robert Lewandowski and his colleagues.
Now the dazzlingly clad Dortmunders face a much bigger challenge. For Bayern this is a grudge match.
Last season they were so confident of lifting the cup in their home stadium, they had commissioned a new museum there, in which a plinth had already been installed ready to accommodate the biggest of all club trophies.
Instead, Chelsea snatched it off away to London. The trauma of that loss was substantial: Bayern do not expect to lose. And they are not coming here to lose again. They are coming to claim what they feel should have been theirs twelve months ago.
A domestic battle fought on an international stage with a cast of hundreds of thousands: London could be in for one night to remember.