Walls have a longstanding relation both with liberty from fear and subjugation to another’s will. After 1945, walls acquired an unprecedented determination to divide. They spread like a bushfire from Berlin to Palestine, from the tablelands of Kashmir to the villages of Cyprus, from the Korean peninsula to the streets of Belfast. When the Cold War ended, we were told to expect their dismantling. Instead, they are growing taller, more impenetrable, longer. They leap from one continent onto the next. They are globalising. From the West Bank to Kosovo, from the gated communities of Egypt to those of California, from the killing fields of old Ethiopia to the US-Mexico borders, a seamless wall is meandering its way, both physically and emotionally, on the planet’s surface. Its spectre is upon us.