Is there a letter from Bohr about the 1950 Nobel prize?

Question

César Lattes had some important participation in the discovery of the the pi meson, but the Nobel prize was awarded to Cecil Powell alone.

There are claims that Niels Bohr left a letter explaining why Lattes wasn't awarded the Nobel Prize. One source: The Oxford Companion to the History of Modern Science:

Powell received the Nobel Prize of 1950 for the discovery, an award that Latin Americans feel should have gone to Lattes. A letter from Niels Bohr, to be opened in 2012, supposedly explains Lattes's exclusion.

Is there any letter from Niels Bohr about this subject?

Answer 1

There's a paper in trying to answer this question On the “Missing Letter” to Lattes and the Nobel Prize in Physics, but the existence of this letter is still unproved.

We can also conclude that there is no longer controversy regarding Bohr and Lattes, at least according to the Bohr Archives, but from the evidences exposed, the possibility of a missing letter still remains. . .