The formation of methane-hydrate precursors at large planar water-methane interfaces has been studied using massively parallel molecular dynamics in systems of varying size from around 10 000 to almost 7 x 10(6) molecules. This process took two distinct steps. First, the concentration of solvated methane clusters increases just inside the aqueous domain via slow diffusion from the methane-water interface, forming "clusters" of solvated methane molecules. Second, the re-ordering process of solvated methane and water molecules takes place in a manner very roughly consistent with the "blob" hypothesis, although with important differences, to form hydrate precursors, necessary for subsequent hydrate nucleation and crystallisation. It was found that larger system sizes serve to promote the formation rate of precursors. (C) 2014 AIP Publishing LLC.