Personality clash between Rex Harrison + Charlton Heston?

It seems that Rex Harrison & Charlton Heston (may they both rest in peace) did not get along at all during the making of the film and, years later when both were cast in Cross Swords, they avoided each other (or at least Harrison avoided Heston). In his autobiography Heston, who for the most part praised hte many British actors he worked with, hinted that Rex was a bit "eccentric" which may have been a nice way of saying they didn't work well together. Anyone else have any info on the bad working relationship between the two?