India, July 24 -- Every British prime minister since the turn of the millennium has, at one point or another, promised to loosen Downing Street's grip on the rest of the UK.

Almost none of them followed through.

Rishi Sunak moved his own children out of central London rather than move government out of it. Boris Johnson dispatched a quarter of the Treasury to a market town and called it revolutionary. Tony Blair and Gordon Brown talked of regional renewal while consolidating decision-making ever more tightly around Westminster and the Square Mile.

Andy Burnham, Britain's new prime minister, is now betting his early premiership on doing what his predecessors did not.

He is physically relocating a functioning slice of the government's n...