It might prove to be the most relatable thing about the Tory leadership hopeful Boris Johnson. The photographs of his messy car – as shambolic as its owner – will be familiar to many of us. The shots of the inside of his Toyota are a still life of slovenliness, featuring empty food cartons, water bottles, crumpled clothes, discarded children’s books, crumbs and receipts. It is either homely or filthy, depending on whether or not you are the sort of person who has to apologise for the mess every time you give someone a lift. What it isn’t is prime ministerly. Margaret Thatcher, a premier with a penchant for dusting, would be appalled.

“I’m in shock,” says Lynsey Crombie, the cleaning expert known online as the Queen of Clean. “A tidy car is a tidy mind.” Crombie only uses her car a couple of times a week, so she cleans it every month. “In a car that you use every day, you should try and spend 10 minutes on it every week. Prioritise getting the clutter and rubbish out. Take out the stuff that doesn’t need to be there – do you really need to have loads of books and a sports kit that’s not been washed?”

She recommends at least a wipe round the steering wheel “with a damp microfibre cloth with a small amount of product. Maybe once a year, look at the upholstery and give that a clean or, if it’s leather, wipe it over every so often. And bash the floor mats.”

She adds that it could be dangerous if a plastic bottle or drinks can were to get stuck under a pedal. There may be other issues if you drive a dirty car. A study by Nottingham University in 2015 tested messy cars, taking swabs from steering wheels, gear sticks and footwells, and found evidence of Staphylococcus and E coli.

“Don’t encourage kids to eat in cars,” says cleaning expert Aggie MacKenzie. “Crumbly biscuits end up everywhere. Always carry an empty carrier bag in the car – it means everything can go straight in the bag and doesn’t get left on the floor.” But she confesses to being fairly relaxed about vehicular orderliness: “When I had small kids, it was kind of my guilty dirty area. If we were ever on a long journey, I’d be up to my knees in discarded papers and banana skins. Then you clear it all up again.”

Still, she thinks Johnson’s car is “hilarious”. It’s partly a class thing, she says. “Toffs don’t care about the mess they live in, and actually why would he need to worry about anything so pifflingly unimportant as the inside of his car? That’s another argument, but I do think there’s something about a state of chaos that’s bound to spill over into his own head and life.”