If the client did not hire the person, as has happened to me before. I ask who he is and who he is here for. If he is there for my clients broker I ask my client if they want him there. If they say OK. OK with me. I constantly ask them what they think about everything to keep them thinking.
If client does not care I tell the person that my inspection is for them and them alone and they cannot follow us.
If the listing broker tries to floow as they often do. The same.
PLease excuse me but I will have to ask you not to follow us, as this inspection is for my client alone. If they want you to know about findings in the report they will tell you in the future.