I know that there is a lot of cynicism about Sundon Loop but having commuted on the Midland Main Line over 20 years and now being resident in the Peak District I feel that its time has still to come with longer, heavier freight trains.
We have still to see the timetable implications of a fairly fast half-hourly Corby-Bedford-St Pancras electric service, alongside doubling of the Slow Lines between Sharnbrook and Kettering. Meanwhile, up north, the re-modelling of the Dore triangle and even the extension of the Buxton run-round will mean that much longer trains can be operated regularly all the way to London.
The much-delayed Cricklewood Aggregates Terminal will presumably draw in additional stone traffic when it finally opens.
Very simply, in future once a loaded freight train has left Corby it cannot be recessed clear of passenger lines until it gets to Silkstream Junction/Hendon other than at Sundon. I know that in theory passenger trains can be switched past it via the Fast Lines but with single ladder junctions this comes at high risk for performance.
We have seen the need for 'jumbo trains' on the Great Western and I think that the Midland Main Line will follow. I realise that this will need some new traction solutions from the FOCs as well.