I like The 39 Steps, I like Rupert Penry-Jones, I like BBC costume drama, but I don't like this.
Why adapt something if you want to write a new story? I don't mind the various adaptations that have come before (all of which tell a different story), but I can't watch this. It's the main female character. She's usually strong and helpful. In this she is too in your face and irritating. Well done BBC. Trying to make the female character stronger has resulted in making her almost unwatchable.
Watch Hitchcock's version for fun, or Kenneth More's for the 50's feel. Even watch the 70's Robert Powell version. It's not so easy on the eye, but it's better than this.