On Saturday 30th September 1967 there was a rail tour of the Stewarts & Lloyds (Minerals) Ltd. lines at Woolsthorpe and Harlaxton, including the stretch of the BR Woolsthorpe Branch between Denton and Casthorpe Junction.
This tour is described and illustrated in the current issue of Railway Bylines (Vol. 24: Issue 8, July 2019) on pages 356-360 Harston & Harlaxton Ironstone Quarries - Notes by Charles A. Rekab. The event marked the imminent replacement of the fleet of industrial steam locomotives by second-hand diesels puchased from British Rail.
This tour is among several that are noted on our page Rail Tour Rambles round Grantham.