William Hartnell flubs the lines "my dear, it was an accepted thing in this age to hire an assassin. Preferably someone dumb."
Following the angle change that occurs shortly after Delos breaks Ian's chains, the shadow of the now retreating first camera can be seen against the rocks.
Nero would not have been addresses as "Caesar Nero"; "Caesar" was not used as a preceding honorific ("Caesar Nero"), but rather was appended to the end of his name. He was "Nero Claudius" and then "Nero Claudius Caesar", with "Augustus" and " Germanicus" being added later.