An item elseweb reminded me:
On railway bridge, over the road between Bankfoot and Birnam in Perthshire, there was for many years, at least 30, a graffito reading "Free Scotland", and more recently has acquired other graffiti including "The Earth is Flat". Three weeks ago driving South from Pitlochry on the A9, near Ballinluig, I noticed that "The Earth is Flat", had been sprayed in black across the back of a road sign. Monday two weeks ago, driving up from Birnam towards Edinburgh on the M90, just before Loch Leven, "The Earth is Flat" was scrawled across the back of another road sign - it looked as though it might have been by the same hand.
Yesterday evening coming up the A1 from the M25, near Stevenage, I spotted "The Earth is Flat" sprayed, in black across the back of another road sign...