Problem is, while a camera is great for showing something did happen, it's not ideal for showing it didn't, all it will show is that the postman didn't come to the door and deliver the parcel during the specific time window of the video you provide.
Can you start small claims proceedings against RM if they don't cooperate?
If RM is saying something was delivered on x date at x time video evidence would be very useful.
I don’t think courier photos are that useful, they often photo the closed door meaning they could just pick the item up straight after.
Agree about threatening them with small claims court.