I can't find the source but I remember hearing of some tale of Margaret Thatcher strolling around London or someplace with some Soviet official. Supposedly he was astounded at the bustling economic activity whizzing about them. He asked her something along the lines of "who is your central planner that has yielded all this?", to which she replied something to the effect of "no, one, this is the Free market operated by individuals, etc etc."

Doing a cursory search for the above, I did find this quote that seemed to capture her sentiments against central planning, to which I think a lot of people use the I, Pencil fable to show the folly that some centralized individuals would have knowledge at all times and all places about what goods and services should be in demand and what they should be priced at and that there's an arrogance to even attempt so much.

"The lesson of the economic history of Europe in the 70's and 80's is that central planning and detailed control do not work and that personal endeavour and initiative do. That a State-controlled economy is a recipe for low growth and that free enterprise within a framework of law brings better results…. And that means action to free markets, action to widen choice, action to reduce government intervention. Our aim should not be more and more detailed regulation from the centre: it should be to deregulate and to remove the constraints on trade.”