That's silly. I think they mean something like a 66 or 67 broke the fishplates on the lines because 31s are lighter than a Shed are a skip.
I hope they don't use the 9 car meridians between Crewe and Skegness because:
A: It's a waste of resources
B: Declassified FC 8)
C: No Chance of Window Hanging
D: Short Platforms at Many of the stations en-route
E: Annoying buzzers/bleepers
When I covered Sleaford-Skegness back in 1999, it was a 153 there and Centro 150 back. Both were packed full and the conductor even opened up the back cab 8)
I don't know why we didn't get the train from Nottingham/Derby Because the house we stayed in was near Clay Cross junction. I seem to remember I persuaded my Mum and Dad to park in Sleaford and get the train
The problem is kinda not with traction but apparently with platforming in Nottingham. Though platform is extremly tight (thank god we have mainly DMUs) Central are worried at loosing another whole platform to allow loco+coaches to pass. That being said, the run-round loops could be used far better to avoid this problem. Alas, the pinch point is west of Nottingham Station where four tracks become two. My mind is still not convinced Network Rails answer is valid.
If you do want proper loco haulage from proper trains where you get steam not diesel particles have a Great Central day