I really expect an app from National Rail to be arriving any time now based on the squirming exhibted in the corrspondense.
Well, nearly: they charge companies for the right to implement the apps for them, who then sell them to the public at £5 a time.
Except when they revoke licenses without warning, and get investigated under competition law. See my other comment further down the page somewhere.
I was sending emails to people about this all last week - if all the people who use the API now get in touch with one another, they might be able to collectively demonstrate just how much NRE is hindering innovation. And then the regulator can step in. (Email me via my website if you're interested!)