Why were the class 46 locos withdrawn so soon?

[70014IronDuke]

Within the context of this thread, something which needs considering is why were Crompton the preferred supplier over Brush?

Perhaps because they produced a higher quality product than Brush?
Brush order book was already full with 31s?
It was part of the politically motivated efforts to spread the manufacturing among a variety of indigenous firms (a la North British saga)?

The Brush gear for the class 46 was only ordered as a fall-back after Crompton deliveries fell behind schedule. They couldn't keep up with the body build rate.

Well, there you go. More evidence that Crompton-Parkinson took time to build a better product vs cheap and cheerful Brush. (Is there a flippant icon?)