The Northampton and Lamport Railway has been working hard to extend its operation south for a number of years and it is now tantalisingly close to being completed! A glance at its website, see....
https://www.nlr.org.uk/boughton-extension/ documents the progress that has obviously, like everything else, been somewhat hampered by the two years of COVID. It looks as if it should be completed sometime this year and that once certification has been achieved trains can operate out and back with the locomotives able to run round, something that has not been able to happen since it opened in 1995.