You're right. It may be a Anthony Trollope thing. I must confess I haven't read any of this books (I usually approach some British authors after having watched a costume drama) so maybe that is what he likes to write: a main story with some tiny ones as interesting, or probably even more, than that main one.

'He knew he was right' came with a documentary about the author butI didn't have time to watch it all. It was narrated by Stephen Fry, which made me happy ;)

I love to rewatch things I love, but it's curious that watching one costume drama, makes me want to watch more ;) It usually doesn't happen to me with movies.