Class AM1 was allocated to the prototype 25kV AC electric multiple units, converted from former fourth rail DC electric stock in 1952 and used on the Lancaster/Morecambe/Heysham route. This route had been electrified by the Midland Railway at 6.6kV AC, but the equipment was replaced with 25kV AC overhead electrification and reopened in 1953 to test the prototype AM1 stock.

The line was closed to passengers and the stock withdrawn in early 1966. Unlike Classes AM2-AM11, which became TOPS Classes 302-311, Class AM1 was withdrawn before it could take its place in the system as the Class 301. However, it was the success of these tests that contributed to the decision to choose 25kV AC overhead electrification as standard in Great Britain (outside the Southern Region).

Previous Use

The carriages coverted to form the prototype units were drawn from former LNWR Electric Units built in 1914 by the Metropolitan Carriage, Wagon & Finance Company for use on the Willesden line fourth rail DC electrification. They had been stored early in World War II after the West London route on which they worked was closed to passengers due to bomb damage.

Formations

Unit numbers were not allocated, but sets were referred to by the last two digits of the MBSO number. The numbers of individual carriages were:

          MBSO     TSO      DTSO
Set 19   M28219M  M29721M  M29021M
Set 20   M28220M  M29722M  M29022M
Set 21   M28221M  M29723M  M29023M
Set 22   M28222M  M29724M  M29024M