I want to make clear that the service is operationally ran very well, and I am sure 4 coaches west of Nottingham are required. However, I travel around 4 times a week east of Nottingham towards Ely/Cambridge, and 2 coaches towards Norwich can be excessive. I'm sure some peak trains are busy, but off peak, midweek, when I travel most, a single Class 153 would be cosy, but sufficient between Nottingham and Ely.
If the 222 trains are freed up by electrification, if the route was diverted to Cambridge, it is my understanding that the speed restrictions wouldn't be particularly problematic, perhaps faster, especially if they could use 125mph on the ECML between Grantham and Peterborough.
Thanks for all the responses though! I was wondering whether any government announcements/franchise agreements etc had mentioned this route, but appears not!
As for the 158 trains - I suppose it is down to personal preference. I find them cramped and claustrophobic with bare facilities. I'd take one of EMT's excellent 156 fleet over a 158!
This is how it looks when I travel:
Sheffield - Nottingham = 4 coaches = 70% full
Nottingham - Grantham = 2 coaches = 60% full
Grantham - Peterborough = 2 coaches = 30% full
Peterborough - Ely = 2 coaches = 60% full, if it stops at March, it can get 80% full for one stop.
Ely - Norwich = 2 coaches = 50% full (based on what I see boarding/alighting).