54 21 31N 00 40 18W
Altitude 262 metres
Estimated Class 4, fails Class 3 on >10% hardstanding within 10 metres. New building might or might not project shadow with sun >20 degrees, in which case Class 5.
UHI, local, facility with buildings and roads, unstable environment. Distance, none.
Evidence of new building and I hope confirming opinion I have correctly located the Stevenson screen.
Large image, click. 2052×913, 252k file
(many images are thumbnails)
Older image left circa 2002, right circa 2009
Note works vehicles on left image, screen is in a poor position.