High- α model with evolving means and standard deviation for azimuthal velocity of the disc-like component. Left: Evolution of azimuthal velocity and azimuthal velocity dispersion as a function of metallicity, capturing a monotonic transition of a chaotic dispersion-dominated state (predominantly made of proto-Galactic populations) to a rotationally supported state with disc-like motion in purple; the velocity dispersion evolution of halo is shown in orange. Centre: Evolution of azimuthal velocity over azimuthal velocity dispersion, V_ϕ/σ_ϕ as a function of metallicity for the disc phase and halo component is shown in purple and orange, respectively. Right: Fractional contribution of disc phase (proto-Galaxy to high-α disc) (purple) and halo-like (orange) GMM components as a function of metallicity. In all the panels, the scatter points show the location of the knots chosen to run our model. The bands are 1 σ errors on the converged weights, velocities, and velocity dispersions. The fractions are computed for an evolving Gaussian for the disc phase and fixed Gaussian for the halo phase when the MCMC is converged.