small detail... the girl is not holding the stake in the air... it is supported by the branch below it (look closely!)
the girl doesn't even have to hold the stake, she just directs it to the right place... and the horse walks along, the centurion only makes sure that it walks correctly... since the horse is trained on command, it's not a problem... yes, sometimes that doesn't work and the stake comes out very quickly (through the chest...but usually the stake is stuck roughly below the navel...sometimes even deeper.