I'm contemplating making a list of men who once seemed improbably elderly matches for the heroine who are now younger than I am - Mr Knightley is on it, of course, and Prof. Bhaer, and I'm the same age as Maxim de Winter, which feels ominous. (edit: how could I forget Edwin Dodd! - though Karen isn't a main character in the same sense as the others...)

I think actors these days do just look younger - whatever combination of personal fitness regimes and advanced make-up, lighting and CGI retouching is going on there means that early 20s and middle to late 30s are often functionally indistinguishable. I was watching the early 80s Barchester adaptation recently and I was struck by how old the younger cast members looked, until I reflected that they were perfectly plausible as people in their mid 20s and early 30s, it was just the standard for actors had changed.