principle, the signal multiplicity could be an important characteristic with which to discriminate between veto events caused by $\gamma$-ray and by neutron backgrounds, due to the multiple, several MeV $\gamma$-rays that result from radiative capture on the Gd loading. Figure \[nvg\_norm\] shows the multiplicity distributions of tagged $\gamma$-ray background signals in the veto detector and of tagged neutron events from calibration data. That the tagging efficiency for background $\gamma$-rays falls more rapidly with multiplicity than for delayed neutron signals is clearly illustrated. However, as is explored in Section \[neutrontaggingefficiency\], exploitation of this difference was not found to be beneficial for the present application, although it might be a useful characteristic in other applications. Successful algorithms for $\gamma$-ray and neutron tagging have been found that use only timing and energy deposition information; these are now described.

![\[nvg\_norm\]The relative efficiencies of the prompt $\gamma$-ray and delayed neutron tags, as a function of module multiplicity. The thresholds for selection of prompt and delayed events are as described in Sections \[gammatagging\] and \[neutrontagging\]. It is solely the multiplicity requirement that is varied. The maximal efficiencies have been normalised to unity to provide a direct comparison. Lines through the points have been added to guide 