In the last of three programmes looking at this most abundant of metals, Justin Rowlatt asks whether the steel-making party is over, or whether a new one is just about to begin. And if, one day, humanity can stop digging this element up altogether.

To find the answers, he speaks to material flow analyst Prof Daniel Beat Muller, sceptical China economist Andy Xie, Andrew Harding of the world's second biggest iron ore miner Rio Tinto, and Ravi Uppal who heads Jindal Steel of India.