24 Hours from St Pancras - How far can you get by train from London in a day?

In the difficult second album after #bus24, comes the obvious follow-up, #train24. Starting from London St Pancras, I'm trying to find the furthest you can get, as the crow flies, by train, before the 24 hours is up.

(The links below contain spoilers about where I got to, obviously, in case you want to watch the video first!)
Route map: https://www.arcgis.com/apps/instant/i...
Timetable: https://twitter.com/politic_animal/st...
Tickets and costs https://twitter.com/politic_animal/st...

The Twitter thread for the whole journey is here   / 1509035606067888129  

If you'd like to hear me talking about the journey on Canadian radio: https://www.cbc.ca/radio/asithappens/...
Read about it in the Daily Mail: https://www.dailymail.co.uk/femail/ar...
The Times https://www.thetimes.co.uk/article/th...
The Independent https://www.indy100.com/viral/viral-t...
In 'Geo' (French) https://www.geo.fr/voyage/quelle-est-...
Or in Expressen (Swedish) https://www.expressen.se/allt-om-reso...