Maynard Keynes is supposed to have said...

what exactly? In my previous posting Robert Skidelsky ended his article by quoting Keynes:

'John Maynard Keynes wrote that "practical men who believe themselves to be quite immune from intellectual influences are usually the slaves of some defunct economist".

I have seen this quote and variations of it attributed to Keynes in several places. Does anyone know what he actually said and where? Or perhaps he said the same thing, more or less, several times in different places?

Perhaps starting a search here might help!