Historically, the UK was run for the benefit of an elite and the regions they lived in, but they discovered that that ran counter to their own interests. They reversed the economic parts of that in Ireland in the 1890s ("Killing Home Rule with Kindness"), and they did so in Northern England after the Wall Street Crash. For example, for part of the 20th century, companies were banned from expanding anywhere outside of deprived regions which caused industrial havoc in the South without providing much long-term benefit to the North. The root problem isn't that government didn't try extreme measure, it's that those measures failed at massive cost, so proposed ones are now subject to much more rigorous scrutiny.
Power in the UK is highly centralised in London, but that's not necessarily bad for regional economic development, e.g. the office ban mentioned above would not have been agreed to by southern devolved regions and the redevelopment of the former East Germany was driven by Bonn (former West Germany's capital city). Competition in government also isn't necessarily good for regional development and the corn laws and free trade that the author credits to Northern England's influence caused another famine in Ireland in 1879. It's also worth noting the North East England referendum of 2004, when London's project of devolving power to the English regions was blocked because Northern English voters overwhelmingly didn't want it.
British manufacturing suffered an unusually steep collapse relative to other western countries in the late 20th century that hit Northern England particularly hard, while the benefits of the slightly later financial services boom were inevitably focused on the country's financial centre in the South. The manufacturing collapse was partially driven by government policies, but not in the way generally thought - for decades, pre-Thatcher governments had been taking fairly regular extreme measures in response to various crises (balance of payments deficits, unbalanced regional development, oil shortages, strikes, etc.), that made life much harder for businesses. But the collapse was mainly driven by the fact that Britain in the second half of the 20th century was mind-bogglingly bad at manufacturing. I suspect that the failure of that entire section of the British economy would be a better starting point for an analysis of what went wrong in Northern England.