There are now 4 million CCTV cameras in the UK and the equipment spend is around £0.5 billion. However, evaluations have focussed on the impact of the installations on crime, rather than the efficiency and effectiveness of the operator. Valuable detection capacity could be lost, without any means to identify the leakage (because events go undetected). A key potential source of leakage is sub-optimal display layout in the control room. CCTV operators are increasingly faced with control room ‘data wall’ arrays displaying multiple CCTV camera feeds across multiple displays. In a survey of 11 local authority and private security CCTV control rooms, operators were faced with a range of 27-520 cameras per operator, with up to 175 feeds displayed simultaneously across a bank of monitors. Where operator evaluations have been conducted, studies have only used single displays, typically depicting socially loaded content (e.g., aggressive ‘flashpoint’ interactions). These kinds of interactions have been shown to be relatively easy to detect. More challenging is detecting static threats such as unattended bags. The modern CCTV operator is increasingly expected to spot changes or suspicious objects that would not attract attention as much as a physical disturbance (e.g. suspicious package). The problem for users of these systems is the potential perceptual overload generated by the constant inflow of huge amounts of visual information. A further complicating issue that has arisen through the continued expansion of surveillance is that the spatial proximity in camera placement is not necessarily represented in the placement of camera feeds in the control room. Whether this lack of spatially coherent organisation in the control room influences detection performance has not been systematically investigated.