By Ben Chu

Policy and analysis correspondent

We're likely to hear a lot about the chancellor's "headroom" in this Budget.

That is the cash buffer the government has to help meet its own fiscal rules and reduce borrowing.

Economists think the buffer might have halved in the last six months from around £24bn to as low as £11bn, in part because of rising interest rates the government has been paying to borrow money from private investors.

The Chancellor, John Healey, might need to raise money to restore it, which would show the government's plan to reduce borrowing by the end of this Parliament is still on track.

At the same time, he is under pressure to find money to help people with the rising cost of living and to fund spending on defence.…