So here it is – a bit of old chain from the dried-up mud floor of our barn. Yes, it was indeed a clever idea for someone to think of links – the way iron can be used to transmit power or resist force, flexibly. So simple in retrospect, and so versatile. Unlike archaeological photos, mine hasn’t got a scale to give you an idea of the size. Looking at this one then, the links might be tiny or huge; but whatever their size, they’re basically the same whether they're being used to tether a ship or decorate a neck, to drag a load or to restrain a slave. It’s interesting to reflect on such simple inventions from so long ago; practical ideas which subsequently enabled enormously important further developments. That's certainly the case for the chain. But it travels further and deeper. As a metaphor, the chain has drawn forth chain smokers, chain reactions, house purchasing chains, mountain ranges and strings of islands, sets of shops or hotels, and just abo...