Right, one step forward..
By removing the rear steps, and air tanks, the cab lifts off. there is enough slack to unhook the cab and bonnet from each other, and the cab will slide backwards with the bonnet top handrails..
The bonnet will lift at the rear, but is held by the metal handrails. Despite using moderate force, these do not seem to pull out from the bonnet. I am almost there. Just not able to see a way to get the front of the bonnet off.