  A first measurement of the polarisation transfer from a circularly-polarised
photon to the final state neutron ($C^n_{x'}$) in deuterium photodisintegration
has been carried out. This quantity is determined over the photon energy range
370~--~700~MeV and for neutron centre-of-mass breakup angles
$\sim45-120^{\circ}$. The polarisation of the final state neutrons was
determined by an ancillary large-acceptance nucleon polarimeter, surrounding a
cryogenic liquid deuterium target within the Crystal Ball detector at MAMI. The
polarimeter characterised $(n,p)$ charge exchange of the ejected neutrons to
determine their polarisation. The new $C^n_{x'}$ data are also compared to a
theoretical model based on nucleonic and nucleon resonance degrees of freedom
constrained by the current world-database of deuterium photodisintegration
measurements. Structures in $C^n_{x'}$ observed in the region of the
$d^*(2380)$ could not be explained by conventional models of deuteron
photodisintegration.
