What is "low cunning"

hi.can anyone tell me what "low cunning" means.it appears from the contexts in which i have heard this phrase that its meaning isnt really derivative from the meanings of low or cunning but that it is a noun phrase meaning something logically simple i.e even though it is syntactically two words it is really just one word. to be precise,a particular example of the use of this word in the following in a book about clear english writing.
in that book,a piece of correspondence is commented upon. the piece of correspondence is this.
"bill and i are fed to the teeth with the way you keep trying to force us into sending our kids into sending our kids,not yours-to a private school when that is completely against our principles. opening a fund for the fees without asking us first was bad enough. Constantly telling the kids how lovely it was going to be was even worse.
Now you have had the audacity to put their names down for,in one case eton, and in the other case,roedean.yuk!
this nonsense has got to stop.until we have had your solemn written promise to leave the education of our children t us,their parents,you will not see either of them again.
and don't bother contacting your precious son,either,because he agrees with me!"
the comments are these.
"well,that certainly told granny,did'nt it?you could scarcely be accused of lack of clarity,conciseness and directness.or that valuable attribute,low cunning."
from the pointed use of low cunning above,it seems indicated that the meaning of "low cunning" is both logically simple and specific.in fact,one even gets the impression that it is a well-worn word. sadly,i have not been able to discover its meaning in dictionaries,including the two volume shorter oxford english dictionary.
should someone respond to this,would you be kind enough to tell me exactly what this word means.that is to say,give me illustrative examples of low cunning,explain how the above qualifies as an instance of low cunning and also if necesary tell me what low cunning is'nt,i.e explain the limits of the word.
expand your description of the word into a paragraph with illustrations etc instead of the pedantic,technical cryptically brief descriptions they give in dictionaries.begging your indulgence
yours
radheshyam