This documentary went out earlier this week but I only caught up with it last night. And I'm glad I did. It's a great study of a brilliant comedian presented by a pretty good comedian and in the light of various recent events it couldn't feel more timely.

Ranganathan explains at the start that he has been an obsessive fan of Pryor since he was a kid and saw his films with Gene Wilder. He later discovered Pryor's stand-up work and got his face tattoo'd on one arm. He thought of having Wilder on the other but was put off by the thought of too much colouring in.

The ex-teacher wants to know what made Pryor so great so goes to Los Angeles and gets his chalk out and comes up with a graphic illustration (see picture). Was it the combination of various factors including his traumatic childhood, being brought up in a brothel? Maybe Ranganathan can never achieve those heights, he wonders, because he was too happy as a kid.

Whatever the reasons for Pryor's genius, this is worth seeing just for the clips. Many of them are taken from Pryor's 1979 Live In Concert video, which may just be the greatest live show ever. Romesh thinks so and, I have to admit, I think it is up there with the best work of Daniel Kitson.

I'm being slightly flippant comparing Pryor to Kitson but what they do share is an absolute mastery of their craft. Pryor just "flows" when he is onstage, an inspired physical mimic as well as a gifted storyteller. We also learn here how Pryor changed from a bland mainstream act into a revolutionary boundary-pushing act. He was influenced by Lenny Bruce of course but also by the civil rights movement and Marvin Gaye. And as is pointed out you can now see his influence all over stand-up. If Billy Connolly is the biggest pre-alternative comedy influence on UK stand-up then Pryor casts the same shadow over American performers.

The clips show the breadth of his material. He can find humour everywhere, even when joking about his childhood beatings. But his honesty is also where things get more complex. He jokes onstage about shooting out the tyres on her car when his girlfriend tried to leave him. It's a very funny routine but...

...and this is where the story suddenly becomes relevant. Can we separate the performer from the man? Ranganathan's friend Suzi Ruffell is not so sure and asks him how he feels about having a tattoo of a wife beater on his arm. It's a tricky issue. The way things are going at the moment a lot of films and TV shows are going to be deleted from numerous hard drives if we can't separate performers' private behaviour from their work.

As the programme comes to an end Ranganathan tries to emulate Pryor by going to an open mic night to work up some new gags. This was how Pryor developed his act. He was prepared to fail and sure enough Ranganathan emulates him by failing too. His newly minted routines prompt the occasional tumbleweed to roll across the stage. But this is how material is born, even though it may have got Chris Rock in trouble this week when he reportedly tried some Harvey Weinstein riffs in a club. If you want to be a rock guitarist you can practice in front of your bedroom mirror. If you want to be Chris Rock – or Richard Pryor – you have to do it in public. And with social media jokes that you realise don't work are suddenly out there whether you like it or not.

But I digress. If you have access to it watch this documentary. Ranganathan is very instructive (you can take the teacher out of the classroom...), the clips are hugely funny and this raises some big issues. If you don't know about Pryor you will learn something. If you do know about him it's still worth watching. Now excuse me while I go and watch Richard Pryor Live in Concert again. 

Watch on Sky Catch Up.