As a journalist, I have specialised in Wales, Welsh politics and devolution for the past 10 years. Devolution, in particular, could be considered a bit niche as subjects go. But suddenly, everyone wants to talk about it because Andy Burnham is making it front and centre of his offer as prime minister. MPs have been falling over themselves saying how great devolution is. I feel like a volcanologist after the Eyjafjallajökull eruption shut down air travel in 2010 – everyone is now talking about the thing I know about. But sudden interest among the general population does not necessarily equal expertise.

Further and more rationalised devolution is an incredible opportunity for the UK. It is the most fiscally centralised country in the G7 – twice as much so as the next most centralised country, Italy. In an international context, it is bizarre that more than 90% of UK tax revenue is collected and controlled by the central government in Westminster. In the US, about half of government spending is by individual states. In the UK, the majority is by the central government. What is even stranger about the UK is that the prime minister is also the equivalent of the first minister of England. It’s like having the governor of Texas also be the US president.

But while devolution is a great opportunity, we need to get it right. In the more than a quarter of a century since Wales got its own parliament, there have been some big lessons that we now ignore at our peril.

First, you can’t just devolve responsibilities, you have to devolve tools. In Wales, devolution is set up to fail. For example, the Welsh government has responsibility for economic development, but many of the key levers for driving economic growth are in........

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