Britain’s bond market will judge John Healey’s first Budget on five things, and its verdict is likely to arrive within minutes of the Chancellor sitting down and the Office for Budget Responsibility publishing its five-year forecasts. Gilt investors will strip the speech back to the size of the buffer, whether the numbers are believable, how much debt is coming and at what maturity, where inflation goes next, and whether the tax and welfare measures can survive Parliament. Get those right and borrowing costs could ease.  [...]