According to R.A. Cooke Track Layout diagrams, Section 10, West Cornwall the siding in the picture closed 16th May 1971. However, from various pictures taken at a later date, the point leading to the yard was still in position for many years afterwards.
Answers from Messrs Munday and Winnen. They are pretty sure that the yard was used by Lee Agricultural Merchants prior to closure - this came in 1984, and afterwards used by Vospers.
A footnote - Hercules seems about the most appropriate name to give any form of motive power - it is most surprising that this loco was chosen to lose its name in favour of Sir Edward Elgar however elegant this name may be.