"I'd only dip into it"

Perhaps you've tried something like this before. One January you moved a decent sum into savings, feeling virtuous, and by March you'd moved most of it back. The three hundred and forty pounds in chapter 1 has that history. So a reasonable objection to everything so far is that you know yourself. Money you can reach is money you'll spend. There seems no point sending it across on payday only to fetch it back on the twentieth.

The objection is a fair one, and the answer lies in how the pot is set up. Two pieces of research are useful here.

Dilip Soman and Amar Cheema studied earmarking among low-income households. Earmarking means setting money aside for a named purpose. They tested two additions to it. One was a visual reminder of what the savings were for. The other was partitioning, which meant dividing the earmarked money into two parts where it would otherwise have been held as one. Both increased saving. People saved more when the money was split into separate parts, and more when the goal was kept in front of them. The authors connect this to earlier research suggesting that every partition is a small barrier. To get at the money you have to open something, and doing that makes you stop and decide.

Ashraf, Karlan and Yin went further, in an experiment with a bank in the Philippines. They offered some customers a commitment account, which restricted the customer's own access to the money they paid in. More than a quarter of those offered it took it up. After twelve months, the savings balances of the customers who'd been offered the account had grown by 81 percentage points more than those of a comparison group who hadn't. These were bank customers in a very different economy from yours, and I wouldn't transfer the number. It does show that many people know they'll be tempted to raid their savings, and that they do better when they can put obstacles in their own way.

You can build the same obstacles at home. None of what follows recommends any particular provider or product. These are ways of setting up a pot so that you stop and think before you take money out.

Keep the pot somewhere other than your main bank. If it sits beside your current account in the same app, moving money back takes two taps and no thought. If it's with a different provider, moving it back takes a login, a transfer and a wait. That's usually enough to make an impulse pass.

Don't have a card on it. A pot should be able to send money to your current account and do nothing else.

Give it a name. Most accounts let you. "Emergencies" or "Washing machine fund" works better than "Saver 2". It's a small version of Soman and Cheema's visual reminder. It's harder to take money out of an account called Emergencies to pay for a weekend away.

Consider two pots when you've got going. One is the cushion, which has to be reachable within a day or so, because emergencies don't wait. A second, for anything longer term, can be harder to reach. Some accounts require notice before a withdrawal, or limit the number of withdrawals a year. I'm describing what exists and not recommending a product, and you'd need to check the terms.

Decide in advance what counts. Chapter 13 will come back to this. Write down, in a sentence, what the cushion is for. A broken boiler qualifies and a sale doesn't. It's far easier to stick to a rule you wrote down calmly beforehand than to one you make up while you're looking at something you want.

And I should be clear that dipping in for the right reason isn't failure. The cushion exists to be used. When the washing machine dies and you pay for it from the pot, the system has done what it was set up to do. Then the next transfers refill it. The three hundred and forty pounds kept coming back because it sat in an unnamed account one tap away, with no rule about what it was for.