That was it!
I'd upgraded Pioneer to a 'Prospector' with additional armour and a weapon.
I then removed the Pioneer gear from Prospector and called it a 'Militia'
The pioneer 'flag' must remain set even after removal of the equipment.
All good now. Needless to say, I went on to ruthlessly crush the enemy with my groups of Knights.
Thanks guys. I'm blown away by the progress to 1.1 - what a game this is going to be 