158843 waits to leave Carlisle with the 16.23 to Chathill. This is an unusual working and is one of Chathill's four daily trains. The station is located on a remote spot of the ECML between Alnmouth and Berwick-upon-Tweed. On arrival at the quiet rural station, that is a long way from anywhere of substantial population, it runs as ECS northwards for a distance of about three miles to Belford crossovers where it returns south again to Newcastle after making another stop at Chathill. This performance occurs twice daily giving Chathill its four trains. All the stations visited in 2017, see their video at....
https://www.youtube.com/watch?v=AHrIufNLs4U and go to about nine minutes in. It's unfortunate that Geoff states several times that it only has two trains per day, carefully studying of the timetable would reveal the early morning pair making the total of four!