House buyers in eastern Europe have recently developed a taste for exotic home finance. Bankers say a significant slice of new mortgages in Hungary are being issued in Swiss francs. Meanwhile, households in Latvia and Romania have developed so much enthusiasm for borrowing in yen that the trend has provoked surprise – and unease – from central bankers half a world away in Tokyo.

The obvious attraction is the interest rate. Switzerland and Japan have among the lowest money market rates worldwide, giving investors a discount on their mortgages worth as much as 5 percentage points a year.