87101
Whilst the first 35 locomotives (numbered from 87001 to 87035, and known as Class 87/0) were identical, the 36th was numbered 87101 and had major equipment differences from the rest of the class. While the 87/0s were fitted with a traditional tap-changer transformer and rectifiers, 87101 had a new thyristor power control system, and spent over a year on test before entering service in 1976. The locomotive, named Stephenson, worked the same services as the standard locomotives for many years, until British Rail was sectorised in the 1980s.
Read more about this topic: British Rail Class 87