  In a previous study, we found that the detached post-common-envelope binary
LTT 560 displays an Halpha emission line consisting of two anti-phased
components. While one of them was clearly caused by stellar activity from the
secondary late-type main-sequence star, our analysis indicated that the white
dwarf primary star is potentially the origin of the second component. However,
the low resolution of the data means that our interpretation remains ambiguous.
We here use time-series UVES data to compare the radial velocities of the
Halpha emission components to those of metal absorption lines from the primary
and secondary stars. We find that the weaker component most certainly
originates in the white dwarf and is probably caused by accretion. An abundance
analysis of the white dwarf spectrum yields accretion rates that are consistent
with mass loss from the secondary due to a stellar wind. The second and
stronger Halpha component is attributed to stellar activity on the secondary
star. An active secondary is likely to be present because of the occurrence of
a flare in our time-resolved spectroscopy. Furthermore, Roche tomography
indicates that a significant area of the secondary star on its leading side and
close to the first Lagrange point is covered by star spots. Finally, we derive
the parameters for the system and place it in an evolutionary context. We find
that the white dwarf is a very slow rotator, suggesting that it has had an
angular-momentum evolution similar to that of field white dwarfs. We predict
that LTT 560 will begin mass transfer via Roche-lobe overflow in about 3.5
Gyrs, and conclude that the system is representative of the progenitors of the
current population of cataclysmic variables. It will most likely evolve to
become an SU UMa type dwarf nova.
