The bacterium that causes bTB,M. bovis, has been evaluated routinely in in GB using traditional genetic methods over the last 20 years as part of surveillance. These studies have the surprisingly restricted distributions of different genetic types to be mapped in Britain - and hence to determine the likely origins of outbreaks that occur in low incidence areas (often associated with cattle movements) however, the classification is not fine grained enough to allow differentiation of local on-farm persistence of disease from that associated with introduction from relatively short distance cattle movements. Our work will use the amazing library of M. bovis isolates held by Defra's laboratory agency and will apply modern whole genome sequencing methods to 2000 carefully selected retrospective samples. We will use samples from recent routine surveillance from over GB, particularly focussing on farms where disease has been persistent, to evaluate the different drivers of persistence that so hamper our control efforts. We will also use samples from the randomised badger control trial where there is unparalleled availability of badger isolates and far more intensively parallel sampled cattle to reveal more details of the complex transmission dynamic between the two species, in order to allow more precise targeting of measures to prevent cattle becoming infected in the future. This data is part of a pre-publication release. For information on the proper use of pre-publication data shared by the Wellcome Trust Sanger Institute (including details of any publication moratoria), please see http://www.sanger.ac.uk/datasharing/