As mentioned earlier regarding the old railway bridge looking on Wikipedia I found this
It is the old Northampton / Market Harborough line. There use to be a station at Kelmarsh down the road.
The disused line is now a linear walk cum Cycle path in parts.
The Northampton and Lamport railway occupy a section of it. I was vaguely aware of their existence but know very little. Wish I had had more time to explore more – maybe next time – when is the next 3mm AGM in Market Harborough!