Hadrian’s Wall, England's border fence from ancient times

Part of Hadrian's Wall, in Cumbria, England. In its heyday the wall stood up to 4.6m high and was 3m wide. Photos: AP

“Looks like we brought the weather with us from California,” the elderly tourist says, pulling on a hat and strolling past me. He disappears up a grass slope, beneath a brilliant, blue sky, his wife beside him.

It’s the first of several American accents I hear that morning. Perhaps they’ve come to see what a real border fence looks like.