  We have recently identified a previously unknown radial migration mechanism
resulting from the overlap of spiral and bar resonances in galactic discs
(Minchev & Famaey 2010, Minchev et al. 2010). This new mechanism is much more
efficient than mixing by transient spirals and its presence is unavoidable in
all barred galaxies, such as our own Milky Way. The consequences of this are a
strong flattening in the metallicity gradient in the disc, an extended disc
profile, and the formation of a thick disc component, all taking place in only
a couple of Gyr. This timescale is drastically shorter than previously expected
and thus can put strong constraints on the longevity, strength and pattern
speeds of the Galactic bar and Spiral Structure.
