Came back from Skegness to Nottingham yesterday on a 3 car ex-Southern EMR Turbostar. Between Grantham and Nottingham we were sat at the very rear of the train in the former first class area. Upon leaving Grantham, the guard announced that passengers for Bottesford and Aslockton should travel in the front two coaches as the doors in the rear coach would not be released due to platform lengths. However at both stations the train was easily fully in the platform (by at least 20m) and there seemed to be no reason for this restriction at all. Can anyone shed any light on it?