This is in fact a Hunslet Class 50550, for-runner of the Austerity 0-6-0STs, only 8 were made HE 2411 through to 2418.

This looks like the area supplying Corby with Iron Ore to me. The loco has a tube for adding water softening tablets so could this be Gunby (Hunslet Works No 2413) at Harlaxton Quarry? Certainly the photographer visited there in 1964.