I just started watching this series. I'm renting Callan Set 1 from Netflix, which is actually the third series of the show (Acorn Media released the 3rd and 4th series because the b/w ones weren't available, but there is an import version called the monochrome years with the early episodes on it).
It's brilliant, intense stuff. It looks very low budget, but the writing and acting and the tension more than make up for it. Great performances all around.
I bought the "set one" which is actually year 3, so I'm doing the same thing you are. I liked it so much that I'm setting it aside, and ordering the first two sets. I want to watch it in chronological order. I've read that the "Lonely" character helped inspire Peter Jackson's design of the Gollum character from the Lord of the Rings. And I see the similarities between Woodward's Equalizer character. Excellent source of a rich and interesting anti-hero. I'm hooked.
shareI don't know whether it was deliberate, but as soon as I saw Andy Serkis/Gollum in the LOTR films I thought: "Russell Hunter/Lonely" ! Very similar looking actors and even similar characters, albeit in totally different contexts.
Currently watching the monochrome years episodes (for the first time since the 60s) and thoroughly enjoying them.