Which was one of the points made prior to the introduction of Mk5s on TP - initially diesel-hauled but swapping to bi-mode or electric with no need for modification of stock once things had got that far.Though naturally a class 93 would bring you precisely no benefit on the Chiltern line (and would not keep to time)... unlike, of course, on an electrified Diggle line, as I doubt I am the first to observe!