Anderssen - Mayet, 1851

I found this a fiendishly difficult problem, mainly because you have to find a distinctly not "normal" move as part of the solution.

The Andersssen in question is Adolf Anderssen, who gave us both the 'Evergreen' and 'Immortal' games as part of his legacy.

This problem arise from a game Anderssen-Mayet, in Berlin, 1851 (same year as the Immortal game, but a different venue and victim).  


I can't find the entire game, but here's the problem, White to Play

White to Play

Perhaps I should add the extra information that the first two moves need to be accurate ( there are no significant ALTs in ChessTempo-speak) but after that mate will arrive.