Budget purdah has been replaced with news management and spin | Larry Elliott

The revealing of titbits once led to a chancellor's resignation - these days details are trailed via press releases

There was a time when budgets were kept secret until the moment the chancellor of the Exchequer stood up in the Commons to reveal the contents of his red box. For weeks leading up to the big day, the Treasury would go into purdah" - a news blackout while officials quietly pieced together a package of measures.

Transgressions of this code were rare and when they did occur they had consequences. Hugh Dalton, the Labour chancellor, had to resign in 1947 after revealing some budget titbits to an evening paper journalist on his way into the chamber, wrongly believing it was too late to get them into print.