Islamic State has declared war on the most important ancient architectural sites in the world. Dan Cruickshank charts its destructive advance and asks what we can do to stop them.

Islamic State has declared war on the most important and romantic ancient architectural sites in the world. Jihadi fighters seek the total destruction of the wonders of the ancient world that gave us writing, the wheel and the first cities. Dan Cruickshank charts the likely course of Islamic State's destructive advance and asks how this can be happening and what we can do to stop them.—BBC Four