As part of the largest upgrade to the Midland Main Line since it was completed in 1870, Network Rail, the UK infrastructure management agency, has notified contractors of the next stage in the electrification programme that will eventually extend wires from London all the way to Nottingham and Sheffield. Aside from serving a number of population centres, the MML is an important freight route, carrying aggregates and cement traffic from the Peak District to London and the South East.