You don't require an economics degree to realise the public finances are up the proverbial creek without a paddle, just as the Government announces it wants to lavish buckets of capital spending on new infrastructure to ‘turbocharge growth'. So how can these two opposites – no money on the one hand, lots of money wanted on the other – be reconciled?

Ah yes, the private finance initiative (PFI), or at least a variation of it. Right now Treasury pointy-heads are wondering whether off-balance sheet spending might again square the circle, providing cash for investment in schools, highways and hospitals while not adding to the public debt and giving the chancellor even more sleepless nights about missing her fiscal targets.