I believe it was 1960. There was a Trains Illustrated article about the last day from an observer at Leicester Central. Locos were generally changed at Leicester. Nottingham and Sheffield (loco change at the latter to electrics) were served by all, elsewhere was a random pattern at places like Loughborough, Aylesbury or High Wycombe.
Replaced by semi-fasts Marylebone to Nottingham Victoria, just 3 a day, but the ex-GC section on to Sheffield had hardly anything apart from the daily Bournemouth-York.
Something tells me that it was reported as a very cold day, and the last day of service in 1960 might have been 31 December.