Einstein letter warning FDR of threat of Nazi nuclear bomb set to fetch $4m

Two-page letter written by physicist and fellow scientist, for sale at Christie's, urged US government to invest in research

A two-page letter written by Albert Einstein warning Franklin D Roosevelt - then the president of the US - that Nazi Germany might harness nuclear research to invent an atomic bomb is going up for sale at Christie's auctioneers in September with an estimate value of $4m.

Einstein's letter - one of two the theoretical physicist drafted in a cabin on the north shore of New York's Long Island with a fellow scientist, Leo Szilard - warned that the German government was actively supporting nuclear research and could make extremely powerful bombs" like the kind that were eventually deployed by the US at the end of the second world war.