  In this paper we consider the previously proposed generalised space-time and
investigate the structure of the field theory upon which it is based. In
particular, we derive a SO(D,D) formulation of the bosonic string as a
non-linear realisation at lowest levels of the semi-direct product of E11 with
the first fundamental representation l1. We give a Hamiltonian formulation of
this theory and carry out its quantisation. We argue that the choice of
representation of the quantum theory breaks the manifest SO(D,D) symmetry but
that the symmetry is manifest in a non-commutative field theory. We discuss the
implications for the conjectured E11 symmetry and the role of the l1
representation.
