Enantioselective surface reactions represent the ultimate expression of selectivity in catalysis, involving stereodirecting processes where only one optical component of a product is formed. A case in point is the hydrogenation of b-ketoesters, which occurs readily on metal surfaces, but with no stereoselectivity so that both optical products are produced. However, catalytic studies show that this reaction pathway can be rigidly controlled if the metal is first modified by pre-adsorption of particular chiral molecules. But how is stereocontrol is achieved by the presence of these chiral modifiers?. Here, we report surface spectroscopic results from chirally modified metal surfaces created under controlled environments. We show that the adsorbed modifiers display rich and complex phase diagrams in which the chemical nature and 2-dimensional organisation of the chiral molecules is a dynamic function of surface coverage and temperature. Of particular interest is that at certain points of the phase diagram, extended supramolecular assemblies of the chiral molecules impose growth directions that destroy existing symmetry elements of the underlying metal and, thus, directly bestow chirality to the achiral metal surface! These supramolecular assemblies also create chiral channels and chiral spaces at the metal surface that we believe are responsible for imparting enantioselectivity by forcing the reactant molecules to dock in one particular orientation, which subsequently directs the hydrogen attack. Our work shows that it is possible to sustain a single chiral domain across an extended surface. The implications of creating structured chiral metal surfaces go beyond catalysis, with potential applications in molecular electronics, non-linear optics and molecular recognition, and we conside general principles which govern the expression of true extended chirality in 2-dimensional space.