energy exceeds 178 keV. Dominated by signal from these photons and supplemented by Bremsstrahlung radiation in the window and the scintillator from $\beta^{-}$ particles with energies in the tail of the distribution that escape the window, the slope and magnitude of the contribution from this component are consistent with expectations [@wright]. The third component in the combined fit to the pulse rate spectrum dominates at higher energies and is of particular relevance to ZEPLIN–III. It is an exponential fit to the background component due to $\gamma$-ray radioactivity from U and Th decay chains and $^{40}$K $\gamma$-rays within shielding and surrounding materials interacting within the scintillator. This includes the contributions from all of the veto detector components such as the plastic and the PMTs, and is dominated by both plastics, despite their low radiological content, due to their high mass. The measured $\gamma$-ray background agrees with predictions from Monte Carlo simulations presented in Ref. [@vetoPaper1] provided that one adopts contamination levels just consistent with the sensitivity of the radio-assays that produced null results, most notably the Gd-loaded polypropylene. This is also consistent with the $\gamma$-ray background observed in the liquid xenon target [@backgrounds]. The radiological activity from the veto detector will 