 Electrification was considered but was deemed to be too expensive as the Thames Line sector would then have to be electrified as well.Another reason electrification did not take place was that some part of the line ran on underground lines, which were electrified as 4-rail 660 V DC, while British Rail preferred 25 kV AC overhead traction for lines north of London.Success of the modernisation implemented by NSE has made it possible for the Chiltern Main Line to compete with the West Coast Main Line between London and Birmingham, and there are now plans to increase speeds and quadruple sections of the line, returning the line to the state it was before the Beeching Axe.