An Australian contact has pointed me to some v interesting stuff about the above (where Mephisto was held for a while). Australian diaries, trench maps, training manual. Map of purpose-built training course, etc. Not only small training ground with large space for spectators, but large-scale exercises/wargames in surrounding country, north of Vaux-en-AmiƩnois.
"Sometimes things that are not true are included in Wikipedia. While at first glance that may appear like a very great problem for Wikipedia, in reality is it not. In fact, it's a good thing." - Wikipedia.