What is the maximum train coach length that currently exists on the through platforms at Wigan North Western station?
11-car Pendolino I guess.
Lengths of the full length platforms are:
P4 (UM) 272m
P5 (DM) 254m
P6 (D&UPL) 268m
An 11-car Pendolino is 264.7m long but in practice down trains can use P5 without problems; I have never gone to the London end of the platform when a 390 is stopped there but in practice public access is only required to the forward most door of the rear vehicle allowing most of the rear car to be off the platform. And P6 has a 10mph speed restriction at its northern end.
I cannot remember what vehicle lengths are specified for the forthcoming TPE units but they will surely be fitted with SDO so even 10x26m would not be a big issue.
My Quail (not the latest one) shows P1 to be 8-9 cars long and the other three through platforms 12 or 13 cars. This will be based on 20m stock though.
Although the Quail books are very useful when it comes to platform lengths it is far better to check the Network Rail Sectional Appendix which is available on-line.