Prince of Wales Theatre audiences complained of cold draughts and hot spots, and of poor air quality, causing sleepiness, with huge differences in comfort between the stalls and circle. Power Plan Services identified several problems. HVAC concept designs and detailed drawings were developed to obtain listed building planning consent. The undersized cooling coils were replaced to improve chiller performance and extract fans adjusted to enhance existing plant capacity. Cool-duct panels were added to the brickwork air-ducts to reduce air leakage. A new stage extract system improved the large-scale air distribution, with bespoke eye lash deflectors addressing local air distribution. As a result, overall “Book of Mormon” complaint levels have dropped.