Burnham wants a new economic model. The cost of government borrowing will judge it before voters do.

Andy Burnham became prime minister yesterday promising to remake the British economy. In his first words outside Number 10 he called it a circuit breaker for Britain and a new economic model, with the biggest changes in the last 40 years. He wants to reindustrialise the country and put what he called life's essentials back under stronger public control. It is a clear turn to the left of Rachel Reeves, who left the Treasury as he arrived.

Who replaces her matters as much as the promise. John Healey is the new chancellor, confirmed by Downing Street as the cabinet was named. He inherits a hard inbox: an economy the forecasters expect to grow just 0.8% this year, high government borrowing costs, and a welfare bill that keeps climbing.

Here is where it reaches your money, and it is closer than it looks. When a government borrows, it sells bonds, called gilts. The rate it pays to borrow is the yield on those gilts, and that yield moves on how safe lenders judge its plans to be. For most of the last two years, investors backed Reeves precisely because she promised to rein borrowing in. A prime minister seen as more willing to spend, and a chancellor not yet tested, is the kind of change that can push borrowing costs up before a single policy is written. That is not a hypothetical. On his first full day, after Burnham said he would use any flexibility in the fiscal rules, the ten-year gilt yield rose above 5%, the highest in the G7, and the pound slipped. Naming Healey steadied it only a little.

You almost certainly hold gilts without thinking about it. Workplace pensions, and especially the default funds that shift towards bonds as you near retirement, hold UK government debt as a matter of course. So do many of the bond funds inside ISAs and SIPPs. When gilt yields rise, the market value of those bonds falls, which is how a change of government can quietly move the value of a pension you have not touched in years. This is not a reason to do anything today. It is a reason to understand that the person moving into Number 11 has a direct line to a figure on your annual pension statement.

The first real test is already arriving. Burnham is reported to be weighing a package worth around 24 billion pounds: making social care free at the point of use, taking Thames Water into public administration, and lifting the tax-free income allowance, with further measures trailed for this week. This is where a new economic model stops being a phrase and becomes numbers: what is taxed, what is spent, what is borrowed. Watch for three things as the detail lands. Does the plan say how it will be paid for, or only what it will do? Does it name a path for borrowing that lenders will believe? And does it mention, anywhere, the thing this paper exists to track, which is what happens to work and wages as machines do more of it? A 10-year plan that is silent on the falling cost of human labour is planning around the weather without mentioning the storm.

Burnham has the mandate of his party and, for now, the benefit of the doubt. What he does not yet have is a costed plan or a proven chancellor. The promise landed yesterday. The bill for it starts arriving this week.