Don’t you wonder where they go? Like odd socks, like teaspoons, like the half dozen biros you bought last week, air and water tokens just gradually disappear into thin air, don’t they?

I am a bit wiser having discussed this mystery with National Car Wash. Director David Henshaw told me: “Every time I get a jet wash back for refurbishment I find 30/40 tokens in the muck at the bottom. Then a lot of them are stolen because they fit other applications. There are a vast array of tokens on the market, probably 30-40 different types in the UK. We stock around 30,000 of them.”

This was good news because I rang National Car Wash in the first place on behalf of Elaine Zamroz from The Halt at Llandrindod Wells in Powys. She had had her machine for a couple of years and was getting extremely low on tokens but couldn’t find the supplier (simple answer was that National Car Wash had moved, the new number is 0151 633 2345 in case anyone else wants to know).

“We’re down to eight tokens,” said Elaine. “We think that people perhaps take two tokens, which only cost them 20p each, then realise they only need one but don’t bother to return the other.”

She sounds a very helpful sort because she often tells customers that, if they take the caps off first and race around a bit, they will be able to do all four tyres on a single 20p token.

There must be very little left in this world that you can actually buy for 20p. Seems quite fitting that it’s just thin air