In his blog, dated 21st  April 2017, George Eustace states

"Planning is another area where change is required.  In the last few years, the Council has had a poor track record in defending Cornwall from urban sprawl and inappropriate development on green field sites"

Lets see if he is willing to acct on his words. If youcan, write to him and ask him to challenge this decision contact him here https://www.georgeeustice.org.uk/contact