PS Churchill was ready to start using Mustard Gas on German cities, till he was advised that England would get the worst of it in retaliation by the Germans if they went that way. It's in Irving's book.
Must be true if it was in a book!!
Irving had the advantage of accessing the primary documents...and being able to read those written in German. Most of the bigfoot WWII historians in the USA and UK managed neither, but simply repeated the post-WWII narrative.