I've been rewatching the whole of Secret Army and I realised that the character played by Ralph Bates in Series 3 crops up in Series 2, played by Michael Byrne – seemingly as the head of Max's cell.
Byrne's performance is very extreme, very often he's drunk and maddened due to his girlfriend's 'betrayal'. Bates is cooler, but with a vindictive edge.
Which portrayal do you think was the best? I go for Byrne's.

