  We study perturbative general relativity with a two-form and a dilaton using
the double field theory formulation which features explicit index factorisation
at the Lagrangian level. Explicit checks to known tree level results are
performed. In a natural covariant gauge a ghost-like scalar which contributes
even at tree level is shown to decouple consistently as required by
perturbative unitarity. In addition, a lightcone gauge is explored which
bypasses the problem altogether. Using this gauge to study BCFW on-shell
recursion, we can show that most of the D-dimensional tree level S-matrix of
the theory, including all pure graviton scattering amplitudes, is reproduced by
the double field theory. More generally, we argue that the integrand may be
reconstructed from its single cuts and provide limited evidence for off-shell
cancellations in the Feynman graphs. As a straightforward application of the
developed technology double field theory-like expressions for four field string
corrections are derived.
