This question is not answered by David Wardale, but by Martyn Bane who researched the turning facilities available within the UK that might be used by the 5AT (see Martyn's website at www.martynbane.co.uk). Martyn's observations were written as follows in 2003:
"Like all tender locomotives, the 5AT will not be designed to run backwards at high speed so it will have to be turned whenever the need arises. Whilst there are now only about 20 turntables available in useful locations, there are still (by our estimate) around 100 triangles located around British railways.
Note: turntables very rarely play an active part in mainline steam operations and where they do there is often an alternative triangle a reasonable distance away. Currently there is a 50 mile tender-first running limit imposed on mainline steam unless there are very special circumstances. Most big locos are limited to 35 or 45mph when running tender first. From a loco operators point of view tender-first running is to be avoided wherever possible. I don't claim the spreadsheet to be exhaustive or 100% accurate - I'd welcome corrections/additions/deletions. I have a few question marks over some of the 106 triangles listed that may or may not have been lifted (my atlas is rather old now). Inverness is the only one I think could limit the loco length."
Incidentally (quoting John Duncan), it is planned that the 5AT to be fitted with air operated throttle, reverser, cylinder-cocks and sanders to allow the locomotive and train to be reversed out of terminal stations via pulse signal control in a DVT (Driving Van Trailer) coach that will run at the rear of the train. Signals will be sent through the lighting control jumpers to a pulse signal control on the locomotive/tender.