I’ve got it, by Jove, I’ve got it. It’s been keeping me awake at night, but I really think I’ve cracked it. I read Tristram Hunt’s article on introducing admission charges to museums many times in the sleepless small hours.

Obviously, I am a bear of very small brain and he is a bear with a brain the size of a honey mountain but, with the rushlight flickering, other than understanding that bushels of loaves and fishes should be removed from the Nicholases Serota and Penny, and left as food parcels on the doorstep of the People’s History Museum, I was struggling.

It just all seemed a bit tricky. It’s clearly unfair if the people of the West Midlands soon have to choose between paying to see their Staffordshire Hoard at the Potteries, or seeing it for free at Birmingham, so I wondered if the most equitable answer wasn’t to round up the Frome Hoard, Winchester Gold, Alfred Jewel, Mappa Mundi, the lot, move them to London and charge there for them, leaving some attractive card-mounted photographs to be inspected for free in the provinces.

But then Hunt says, “naturally”, schoolchildren and students, and residents once a week, should get in free, and I started to toss and turn again. What about these pesky foreigners the government says keep signing up to fake courses? Do they get in free as students?

And what about Russian billionaires living for a day or so a year in an entire street of knocked through mansions? Do they get in free too if they turn up on the right day with their electricity bills?

Shouldn’t there be a sliding scale for schools, so that pupils from a bog standard comprehensive get in when the doors open in the morning, but the Oratory lot are only let in free five minutes before closing time?

And then it came to me: a way of targeting charges so that only adults, all in work, all guaranteed regulars and so unlikely to be put off returning, pay. Simple to administer, simple to collect: charge the museum staff for admission.