  We present the discovery of a magnetic field on the white dwarf component in
the detached post common envelope binary (PCEB) CC Cet. Magnetic white dwarfs
in detached PCEBs are extremely rare, in contrast to the high incidence of
magnetism in single white dwarfs and cataclysmic variables. We find
Zeeman-split absorption lines in both ultraviolet Hubble Space Telescope (HST)
spectra and archival optical spectra of CC Cet. Model fits to the lines return
a mean magnetic field strength of approximately 600-700 kG. Differences in the
best-fit magnetic field strength between two separate HST observations and the
high v sin i of the lines indicate that the white dwarf is rotating with a
period ~0.5 hours, and that the magnetic field is not axisymmetric about the
spin axis. The magnetic field strength and rotation period are consistent with
those observed among the intermediate polar class of cataclysmic variable, and
we compute stellar evolution models that predict CC Cet will evolve into an
intermediate polar in 7-17 Gyr. Among the small number of known PCEBs
containing a confirmed magnetic white dwarf, CC Cet is the hottest (and thus
youngest), with the weakest field strength, and cannot have formed via the
recently proposed crystallisation/spin-up scenario. In addition to the magnetic
field measurements, we update the atmospheric parameters of the CC Cet white
dwarf via model spectra fits to the HST data and provide a refined orbital
period and ephemeris from TESS photometry.
