Over 4 million people use the London Underground each day. Although not often visible to customers, during the night thousands of people are also busy at work to ensure that the signalling, tracks and other critical infrastructure is maintained and upgraded to meet increased demands placed on the Tube network. London Underground (LU) maintains hundreds of facilities across the English capital that provide access to tracks and tunnels, and possesses highly specialist equipment and spare parts needed for both routine maintenance and improvement work. The loss of specialist equipment through theft can impact the entire network.