Just how accurate do you think docu-dramas are ?

I have always wondered about Docudramas as:The Queen,thirteen days,Nixon etc,,,, They rely heavily on depicting what transpired behind close doors.
How accurate do you think they are as I doubt the people involved would ever divulged what really happened and what exactly was said.
*For all we know the queen met with prime minister Blair in her robe and told him she was glad princess Diana was gone as she was a royal pain in the @$$,,, all while sitting on his lap !!
Knowing, Kennedy must had a few girls under the table while conducting his meetings!