There were all sorts of supposed clues about this circulating in the late 60's- everything from 'clues' on songs like the one Drummond mentioned to 'hints' on the cover of Abbey Road. Ridiculous nonsense, though I have to say one could almost be forgiven for thinking this if basing it on much, not all, but much of the guy's post Beatles output: such as songs like "Freedom," "Ebony &Ivory, "Say, Say, Say" and "Silly Love Songs".
