  GRB061007 is the brightest gamma-ray burst (GRB) to be detected by Swift and
is accompanied by an exceptionally luminous afterglow that had a V-band
magnitude <11.1 at 80s after the prompt emission. From the start of the Swift
observations the afterglow decayed as a power law with a slope of
\alpha_X=1.66+/-0.01 in the X-ray and \alpha_{opt}=1.64+/-0.01 in the
UV/optical, up to the point that it was no longer detected above background in
the optical or X-ray bands. The brightness of this GRB and the similarity in
the decay rate of the X-ray, optical and gamma-ray emission from 100s after the
trigger distinguish this burst from others and present a challenge to the
fireball model. The lack of a cooling or jet break in the afterglow up to
\~10^5s constrains any model that can produce the large luminosity observed in
GRB061007, which we found to require either an excessively large kinetic energy
or highly collimated outflow. Analysis of the multi-wavelength spectral and
high-resolution temporal data taken with Swift suggest an early time jet-break
to be a more plausible scenario. This must have occurred within 80s of the
prompt emission, which places an upper limit on the jet opening angle of
\theta_j=0.8deg. Such a highly collimated outflow resolves the energy budget
problem presented in a spherical emission model, reducing the isotropic
equivalent energy of this burst to E_{\gamma}^{corr}=10^{50} ergs; consistent
with other GRBs.
