I suppose if they had been deemed suitable for the Robin Hood Line, we might have got Pacers on other East Midlands services such as Derby-Matlock and Nottingham-Skegness.Years ago a retired Nottingham guard told me that he and a driver conducted an Eastern Region crew on a pacer (not sure if a 142, 143 or 144) on the soon to be opened Robin Hood line in the 1990s, not long after they had learnt it. Don't know if this was the initial service from Nottingham to Newstead or one of the later extensions, Mansfield/Worksop, but he did tell me it was the latter days of BR.
They were told at the time that this was to assess the suitability of pacers for the service.
Happily, it was obviously decided they weren't suitable.
I wonder if the Class 140 was ever tested on the Matlock line? The Matlock branch (and the Wirksworth branch when it was part of the BR network) has a long history of being used as a testbed for new units.
I also wonder if BR ever considered using Pacers on the Thames Valley branches or Anglia local services.