I came up with some surprising results. I was expecting solid stone walls and that is certainly not what I found. The first three pics are of a surviving wall that is somewhere near the site of the Battle of Omdurman; the last picture of a French Foreign Legion fort in Tunisia. The latter is much more akin to what I was expecting. I remember when reading a copy of Touching History,Paul Darnel's scenery making booklets in the Sudan and WWII Edition and seeing something he had made similar to the fortifications in the first three pics.
In the scan below it's clear that I've been barking up the wrong tree. Possibly there were more permanent fortifications at Khatoum, Possibly with a more north African influence but it seems clear that the majority of the fortifications would have been of the structure oulined in the photographs and Paul Darnel's creation.
Fortifications near Omdurman
French Foreign Legion Fort
At present I haven't got the room to do much work on this project but it would be interesting for future reference. I'll also be making quite a few Adobe type dwellings, possibly even a model of the Mahdi's tomb.