You used to know you were getting older when policemen looked young. Now the benchmark is the prime minister.

When Labour swept to power in 1997, my sister (who’s 10 years older than me) said it was a shock to realise the new PM was her own age. It was a rite of passage, like voting for the first time or qualifying for a free bus pass.

I now know how she felt. If David Cameron wins the next general election – far from certain but a strong possibility – I will be older than the premier. Not to mention eight years older than the likely chancellor.

I’ve suddenly warmed to fiftysomething Gordon Brown and sexagenarian Menzies Campbell!