  We present observations of GRB 060124, the first event for which both the
prompt and the afterglow emission could be observed simultaneously and in their
entirety by the three Swift instruments and by Konus-Wind. Thanks to these
exceptional circumstances, the temporal and spectral properties of the prompt
emission could be studied in the optical, X-ray and gamma-ray ranges (up to 2
MeV). While the X-ray emission (0.2-10 keV) clearly tracks the gamma-ray burst,
the optical component follows a different pattern, likely indicating a
different origin, possibly the onset of external shocks. The prompt GRB
spectrum shows significant spectral evolution, with both the peak energy and
the spectral index varying. As observed in several long GRBs, significant lags
are measured between the hard- and low-energy components, showing that this
behaviour extends over 3 decades in energy. The GRB peaks are also much broader
at soft energies. This is related to the temporal evolution of the spectrum,
and can be accounted for by the softening of the electron spectral index with
time. The burst energy (E_iso~5x10^{53} erg at z=2.297) and average peak energy
(E_p~300 keV) make GRB 060124 consistent with the Amati relation. The X-ray
afterglow is characterized by a decay which presents a break at t_b~10^5s.
