  Despite the recent advancements in the field of galaxy formation and
evolution, fully self-consistent simulations are still unable to make the
detailed predictions necessary for the planned and ongoing large spectroscopic
and photometry surveys of the Milky Way disc. These difficulties arise from the
very uncertain nature of sub-grid physical energy feedback within models,
affecting both star formation rates and chemical enrichment. To avoid these
problems, we have introduced a new approach which consists of fusing disc
chemical evolution models with compatible numerical simulations. We demonstrate
the power of this method by showing that a range of observational results can
be explained by our new model. We show that due to radial migration from
mergers at high redshift and the central bar at later times, a sizable fraction
of old metal-poor, high-[alpha/Fe] stars can reach the solar vicinity. This
naturally accounts for a number of recent observations related to both the thin
and thick discs, despite the fact that we use thin-disc chemistry only. Within
the framework of our model, the MW thick disc has emerged naturally from (i)
stars born with high velocity dispersions at high redshift, (ii) stars
migrating from the inner disc very early on due to strong merger activity, and
(iii) further radial migration driven by the bar and spirals at later times. A
significant fraction of old stars with thick-disc characteristics could have
been born near the solar radius.
