This is the Review of an enforcement database operated by the Metropolitan Police Service known as the Gangs Matrix. The Review was a specific commitment in the Mayor’s Police and Crime Plan and also in his 2016 election manifesto. The Review, the most comprehensive ever conducted into the MPS Gangs Matrix, combines analysis of those on the Matrix; interviews with practitioners and those in communities affected by the Matrix; and detailed discussions with a Reference Group of practitioners and subject matter experts. The Review also takes note of the recent investigation by the Information Commissioner’s Office (ICO) on the Matrix.