The patchwork of power across the UK’s nations and regions can be hard to follow. Mace’s Devolution Index provides your guide to the movers, shakers and legislative power-takers who have taken back (some) control from Westminster – and, in some cases, would like a whole lot more.

To paraphrase John Lennon, you say you want devolution - well, you know, we all want to change the world. Since the D-word entered the Westminster lexicon in the late 1970s, policymakers and academics seem to have spent as long debating how to apply it to UK politics as they have enacting it. Half a century after that - and almost 25 years after referendums in Scotland and Wales first established legislative outposts in the nations - devolution remains as hotly contested as it is influential on our politics.

With two devolved parliaments, a national executive and ten mayors of the English regions, keeping track of who really matters has never been a more complicated task.