Premise (if you want to watch from the beginning, know that there will be some spoilers after the first paragraph)
The show starts out with Blake being told that he once lead an entire revolution, and he was just recently brainwashed to apologize for all his rebellious acts and then brainwashed again to not remember any of it, including the apology. He sneaks off to a meeting, and once being overloaded with this information, catches some here. He comes back to see everyone in the rebel meeting killed, and he's caught and tried as the murdered and traitor. He's sent to prison on a ship with a bunch of other convicts, and on course a strange space ship is discovered. Blake and 6 others are ordered to explore the ship, which welcomes them and helps them escape. Hence, Blake's 7! Crazy adventures across the universe ensue.
As time goes on, the team of people change and after a point some of the team starts to die off. And then the producers take a big risk. They kill off Blake. That's right, the guy who the show is named after gets killed! And a new leader takes hold...
and he is an asshole.
This is Avon. Avon is one of the original members of Blake's 7. He's one arrogant, devious, conniving bastard, but he's also smart. Blake keeps him around for the cunning advice, although you never really know who Avon is rooting for, other than himself. He's a great example of someone who in the D&D universe is labeled as True Neutral. He'll stick together if it's in his benefit, but once his needs are calling loud enough he'll skip out. He was a wild card that you had to worry about. And then to top it off he was the captain of the ship!
THIS is what makes great TV. A character who is skilled and flawed at the same time. The crew ends up depending on Avon even when he clearly tries to abandon them from time to time. He's super secretive about what he does, keeping everyone--especially the viewer--on their toes.
This is why reality TV is gaining speed. It's because writers are having a hard time making the complex characters that keep us watching, so instead they use psychology to set up regular people to have complex reactions. Writers, step it up! Give us some Avons! Give us somebody who we can empathize with even though he's a dick! Give us a conflicted woman who isn't conflicted between work and popping babies! There's more to being a woman than that! Give me some humanity!