Exactly. Tom has pointed out how running costs are hardly a significant factor on the preserved railway, so we should eliminate them from consideration. I suggest this means its largely irrelevant whether a locomotive can do the required work with 5% to spare or 25% to spare, just so long as it can do the work. And that also means that its quite irrelevant whether the locomotive would be better suited to different work that no longer exists. What's important, I suggest, are - firstly net build and overhaul costs, net costs being those after excluding what cash and volunteer manpower the locomotive can bring with it, and - secondly traffic generation, what visitors the locomotive can attract over and above another type. And of those two, I rather suspect the first is king, but it is the net cost that needs to be considered, not gross. No point in having the cheapest and easiest to maintain locomotive in the world if no-one will volunteer to finance or work on it and everything must be done from revenue by salaried staff.