The DAPPLE (Dispersion of Air Pollutants and their Penetration into the Local Environment (www.dapple.org.uk) project is a consortium of six universities, which involves a multidisciplinary approach to characterise relatively small-scale urban atmospheric dispersion. This is achieved by a combination of Wind tunnel modelling studies, computer simulations, fieldwork studies and analysis. One of the main objectives of the consortium is to complement the relatively limited data available for short range dispersion in European Urban centres. Data concerning movement of material through the urban canyon network can be used to inform local air quality management, emergency response management and regulatory models. The work here describes the rationale and methodologies and instrumentation which underpin a series of dispersion experiments carried out in Central London during 2007 and 2008. These include multiple simultaneous point source experiments and some novel experiments using a moving line source.