While many of the documentaries marking the 20th anniversary of Diana's death have been revealing, entertaining, and a reminder of a wonderful person, this one fails for one reason: they used an actress to play Diana, which is a singularly impossible feat to perform. Acting means that one has the ability to suspend the disbelief of the audience, disbelief that they are an actor playing a role: in other words, the audience forgets they're looking at an actor, and are absorbed in the tale that is being spun. That is not possible when the person you're playing is so famous. The same thing happens with Marilyn movies. Michelle Williams playing Marilyn?! Whoever thought that up should be fired: there's not a single cell of anything in Michelle Williams that reflects MM. Same with anyone who tries to play Diana: all you're looking for is how wrong she is, how not Diana she is, how she doesn't sound, look, move like her---and the reason is that Diana was a rare creature whom no one could emulate. Same as Marilyn.
Having got that obvious comparison/failure out the way, the content was good and yes, it's always good fun to watch a documentary and constantly point out how wrong the actress is for trying to play the role they're playing!!