[Retros] Original by Kari Karhunen

[Olli Heimo]

Hi! I showed some our discussions to Kari Karhunen. He is IM in solving and he suggests the following problem claiming that it is sound. I have not yet solved it. Olli. Solutions please.

Kari Karhunen, original for retro mailing list.
White wants to avoid any possibility that the game ends with 5. - NxR#.
Which was the first move by White.