Departmental Use
After the units were withdrawn from passenger service, they continued to be used by the Research department for further tests. For this purpose, the units and individual carriages were all renumbered into the departmental series. Two power cars were teamed with a newly built pantograph trailer and became TOPS Class 920, number 920001. This was then used for the development of classes 313-315. The remaining cars were formed into two four car sets and became TOPS Class 935, numbered 056 and 057 in the Southern Region departmental (non-revenue earning) unit series.
Read more about this topic: British Rail Classes 445 And 446