First of All, in terms of Rating, I would just give this BBC mini drama a 3 out of 5, which means it is just average. However, a story/ film or whatever could at some point touches you no matter how bad/ good it is. Most of the art work in my opinion worth a review, rating does say something but it can't say it all. Okay, I'm gonna stop rambling, get back to the topic.
This mini drama, to me I would treat it as a film . It is about an encounter between 2 person on their daily commuting train. They get to 'meet' each other through a dispute over a seat. Then followed by an apology. Then the affair. The discovery / confession. The fight. Finally the reconciliation in both families that were affected.
Such fairy-tale like ending might or might not happen in real life, you just can't judge it by logic. Anyways, like the detailed portrayal of everything that was once and still very familiar to me. The story can get quite engaging as it progressed. However, I feel the scene shoot at seven sister a bit redundant .. don't know why it was there. The ending lacks creativity, but it can be unpredictable as well to some viewers. In fact, I think such happy ending was a great relief to me, as I think Carl has been a decent men therefore I don't want he get such punishment over this.
Bellow are 2 reviews I found, second one was interesting though being a bit harsh.
http://www.telegraph.co.uk/culture/tvandradio/10558876/David-Nichollss-The-7.39-Railway-romance-or-a-train-wreck.html
Again what I really like about this is it reminds me those days I spent nearly 5 hours commuting from Waterloo station to work. It was just as clear and fresh as what happened yesterday, but also quite distant that was just like in a dream. So you know why I don't want to rate this film? Sometimes it was just all beyond rating.
Sorry that I am getting nostalgic again, but do watch this drama if you can. I also attached another link about extreme commute in real life. :)
http://www.bbc.co.uk/news/magazine-25551393