the liquid at which the interaction took place. ZEPLIN–III derives its own trigger either from [*S1*]{} or [*S2*]{} depending on the energy deposit and hence digitises timelines $\pm$16 $\mu$s either side of the trigger. Consequently, the veto data acquisition must do likewise (in fact a slightly wider pre-trigger timeline is adopted, -20 $\mu$s). The trigger point in ZEPLIN–III corresponds to the 17.7 $\mu$s mark in the veto detector timelines. For [*S1*]{} triggered events, any prompt coincidences in the veto detector will appear as a peak at approximately 17.7 $\mu$s. This is illustrated in Figure \[starttime\_merge\] showing the times of veto detector pulses recorded in background data, having been triggered in slave mode by ZEPLIN–III. A single peak with a FWHM of 226 ns corresponding to prompt coincidences with [*S1*]{} triggers is visible above background (insert) and the region around this peak has been enlarged. The events triggered by [*S2*]{} have [*S1*]{} signals preceding the trigger point and [*S1*]{} coincident pulses in the veto detector are distributed in the region prior to the prompt peak. The lower level of signals occurring after the prompt peak, unrelated to the trigger signals in ZEPLIN–III, are random background seen in the veto detector itself.

