Taking a 45-year view of bond markets can insure us against tomorrow's shocks

What will the UK look like in 2070? The population will rise by 7 million, hitting 76 million, the UN predicts.

- Richard Davies

But it could shrink to 65 million or swell to 88 million, depending on what happens with birth rates and immigration. Temperatures may rise 1C, if countries stick to their Paris Agreement promises, but could be up 2.5C if they do not. Computer chips will be 6m times more powerful, but only if Moore's Law holds. On a 45-year view, it's safe to say things are uncertain.

Except when it comes to UK debt. The British government's IOUs currently total £3tn, a little over 100% of GDP. They include bonds that mature - that is, must be paid back - in 2071 and 2073. Forget about death and taxes: the only thing certain about the future is debt.