The Midland Railway experimented with electrification on its Heysham–Morecambe–Lancaster line in Lancashire, England.
The three DM cars were built by the MR at their Derby Works and were 60 feet (18.29 m) in length.
Of the six DT cars, four were built new by the MR at their Derby works, while the other two were converted from existing hauled stock compartment coaches.
The line voltage remained at 6,600 but the frequency was altered to 50 Hz and this was transformed and rectified on the trains to supply DC traction motors.
This experiment led to the introduction of the 25 kV, 50 Hz system as standard for new electrification on British Railways.