309 of these loco's were built as part of the British Rail Modernisation Plan. First constructed in January 1959, the last of the loco's were completed in November 1965.
In the 1980's many Class 37's were extensively refurbished and split into several sub-classes, these being 37/0, 37/3, 37/4, 37/5. 37/7 and 37/9.
More detailed information on the sub-classed will be given with each gallery.