We present an integral representation for the parity-even part of the
two-loop six-point planar NMHV amplitude in terms of Feynman integrals which
have simple transformation properties under the dual conformal symmetry. We
probe the dual conformal properties of the amplitude numerically, subtracting
the known infrared divergences. We find that the subtracted amplitude is
invariant under dual conformal transformations, confirming existing conjectures
through two-loop order. We also discuss the all-loop structure of the six-point
NMHV amplitude and give a parametrization whose dual conformal invariant
building blocks have a simple physical interpretation.Comment: 58 pages, 8 figure