Just wondering if there are any completely isolated sections of the NR network where it is not possible to get a train to run over. In other words, could a train on National Rail tracks theoretically get to anywhere else on Nathional Rail tracks in the country? (Ignoring issues about it not being cleared, lines not electrified, etc. or connections not being signalled). SOme branch lines are often run as an isolated shuttle, but do they all have connections to the mainline?