similaritys of class 56 and 47 design and class 37 / 40 design

[wessexrailwaysdude]

Just something i was curious of.

The class 56 externally looks similar to the class 47 and i was wondering if this was a design that co-incedental or if the design was based on the class 47 in a similer way the class 66 are based on the class 59.

(Class 66's could be refered to as a modified idea of a class 59 but the reason the two look similar is because GM choose the body shape of the class 59 and some other items such as cab design knowing they would work in the UK and then built a new locomotive around the class 59 shape / design)

I wondered if something similar was going on with the class 56.

Only info i can find on this is a class 47 was used to test an engine design for class 56's although this in its self does not actually say thats why a class 56 looks similar to a class 47.

Any info on this would be useful.

Same again with class 37 and class 40....