I usually don't mind Bidisha, but never travelling on GW again for that??
I agree that loud actual conversation can be more intrusive than a quiet mobile call. But I also think if you travel on British trains regularly, you don't expect every journey to be perfect, and you don't expect the quiet carriage to be totally silent. It's nice to get some work done, but I wouldn't necessarily expect perfect working conditions, and sometimes you have to accept today is one of those day - having got some of it done is a bonus.
But if someone was annoying me that much, I would ask them to tone it down myself, although possibly not along the lines of, "Don't you know I am a jolly important journalist," more, "I'm trying to work, so could you keep the volume down a bit, please?" If they got arsey about that, that might be when you'd involve the conductor. But nore likely, I'd give up and sit back and listen in abd shamelessly gather decent snippets for a future good article. Which this one wasn't.
And if it was taking so long to get from Reading to Paddington, some noisy passengers would be the least of my gripes.
P.S. Dear Huffpost/Guardian, among my many skills is my ability to waffle on aimlessly for several paragraphs (see above for example.) I'm ready for a new job, and I reckon I can do better than what you published there, so feel free to contact me. 