Matthieu Laneuville’s paper, co-authored by John Hernlund, Nicholas Guttenberg, all at ELSI in Tokyo, and myself has been published in Phys. Earth Planet. Inter. and is available online. In this paper we present results of a model of evolution of the deep Earth including a basal magma ocean that is initially stably stratified. Fractional crystallisation from the top provides negative compositional buoyancy acting against the initial stratification and slowly mixing the basal magma ocean, which delays the cooling of the core and lower mantle.