You’ve probably read or heard a lot about how prices keep going up for gas, food, clothes, electronics, and pretty much everything else. That’s called inflation, and it’s a problem for nearly everyone. But here’s a story about deflation—and it’s a problem only if you live in Great Britain and your parents, or maybe even you, drive a big S.U.V.

Since March, a group of anonymous activists has been prowling the streets of Britain’s cities at night, dressed in dark clothes and avoiding streetlights and security cameras. Their mission: letting the air out of the tires of Range Rovers, Mercedes G-Classes, BMW X5s, Audi Q8s, and other tank-like, gas-guzzling, road-hogging S.U.V.’s.

The group is called Tyre Extinguishers. (“Tyre” is how British people spell “tire.” We suspect the name is meant to be a pun on “fire extinguishers,” even though Britons don’t spell “fire” as “fyre.”)

Tyre Extinguishers claims to have no leaders or formal organization, only a Web site that declares, “We are people from all walks of life with one aim: To make it impossible to own a huge polluting 4x4 in the world’s urban areas.”

(A 4x4 is a car with four-wheel drive, which is the case with most S.U.V.’s; the two terms are sometimes used interchangeably, though that isn’t really correct. For the record, Air Mail Pilot disapproves of linguistic imprecision.)

“We are defending ourselves against climate change, air pollution, and unsafe drivers,” the Web site continues. “We do this with a simple tactic: Deflating the tyres of these massive, unnecessary vehicles, causing inconvenience for their owners.”

Over the past three months, the group is reported to have flattened the tires on more than 3,000 cars. Anyone can join in. “Target posh/middle class areas,” the Web site advises would-be deflaters hunting for S.U.V.’s. “You won’t have to walk far to find one.”

(For the record, Air Mail Pilot does not approve of even minor vandalism, but does find this whole endeavor appealingly spirited.)

Last week a reporter for The Times of London went on a mission with two young Tyre Extinguisher activists in the leafy North London neighborhood of Hampstead. The reporter met up with Hugo and Josh (not their real names) at 11 at night. They had already deflated the tires on 15 cars.

Following Tyre Extinguishers’ rules—an honor code, of sorts—they left a standardized leaflet on each vehicle, which reads in part, “We have deflated one or more of your tyres. You’ll be angry, but don’t take it personally. It’s not you. It’s your car.”

That night Hugo and Josh had only printed out 23 total leaflets, which meant they could hit only eight more cars. When better organized, they claim they can let out the tire air on upwards of 50 vehicles. “It’s a bit Keystone Cops,” Josh confessed, referencing a silent movie series that was sort of the Brooklyn Nine-Nine of its day.

The two activists showed the reporter how the deflating is done. One of them opened the valve on a rear wheel of a Mercedes G-Class, put a small dry bean into the valve cap, and screwed it back on so that the bean was pressing down on the little pin in the center of the valve. This let the air out slowly, which had the benefit of not making a loud, neighbor- or cop-attracting hiss. It also gave Hugo and Josh time to get away.

The two were using dry mung beans that night. The Tyre Extinguishers Web site recommends lentils, but adds, “You can experiment with couscous, bits of gravel, etc.”

The campaign seems to be working, at least on a small scale. The Times reported that the group has received letters from at least two annoyed victims asking which smaller car models would be safe from deflation. —Bruce Handy

The Bank of England will not agree to bring down inflation rates, which have recently reached a 40-year high. But what Andrew Bailey, the head of the bank, will do is explain what inflation is. To make the concept easier and sweeter, Bailey and a few economists at the Bank of England are using Freddos—Cadbury chocolates shaped like frogs—to teach people the concept of inflation.

Partly because of rising inflation rates, British people’s gas and electricity bills have increased by 54 percent. Naturally, people are frustrated. Bailey wants people to understand exactly why their bills have increased. So, in addition to running the Bank of England, he’s also helped the bank publish a book titled Can’t We Just Print More Money?

Throughout the book, co-authors Rupal Patel and Jack Meaning use the price of Freddos as an example. In 2002, a Freddo cost 14 cents; today a Freddo costs 33 cents. It’s the same milk chocolate frog, so why does it cost more? As they explain, printing more money means that every existing coin and dollar will be worth a little bit less. Eventually, this will cause the price of delicious chocolate to rise.

Jack, who works in the Bank of England’s Strategy Division, says the book is important because everyone, even kids, should have an educated opinion on matters that impact their day-to-day life. “It’s quite easy in the current environment to have a conversation about inflation,” he told The Times of London. “[B]ut if people don’t understand what those drivers are or why things are happening, how are they supposed to effectively make a judgment on whether we’re doing the right thing or the wrong thing?”

Three thousand copies of the book have already been given to state schools around England. All the money the books make will go towards funding education programs, as well as to printing more copies so it can go in even more schools.

So, dear AIR MAIL Pilot readers, we’ll leave you with a trick question: Put 33 cents in your piggy bank or buy a chocolate frog? —Clara Molot

A note to AIR MAIL Pilot readers: if you visit a farm and meet a horse or pig, think before you speak. Turns out, you can make their mood better or worse.

While we’ve always known that dogs and cats can detect how humans feel, last week researchers from the University of Copenhagen discovered that horses and pigs can sense our feelings, too.

To find this out, a group of scientists rounded up pigs and horses—both wild and domesticated ones—to test if, and how, they reacted to positive or negative noises made by people. (They also tested to see if the animals reacted differently to positive or negative grunts from their own species, but AIR MAIL Pilot doesn’t speak pig or horse so we will set that part aside).

To start, the team recorded an actor speaking gibberish in both a happy tone and an angry tone. While loudspeakers blared the babble, researchers monitored the animals to see how much they moved, if they stopped eating, if they flattened their ears, and if they tilted their heads to hear the sound better.

Much like people, the animals didn’t like hearing the angry human voices. When the furious gibberish started, both the horses and pigs scuffled agitatedly. But when the friendly gibberish played, the animals ambled around the room as usual, oinking, neighing, and scratching without a care.

The study revealed that the animals can not only tell how humans feel, but also that humans’ moods affects them. “Our voices have a direct impact on the emotional state of animals, which is very interesting from an animal welfare perspective,” Elodie Briefer, a behavioral biologist at the University of Copenhagen, told The Times of London. “If animals are initially spoken to in a more positive, friendly voice, when met by people, they should react less. They may become calmer and more relaxed.”

Overall, the wild horses and pigs were the least perturbed by the angry sounds. Don’t try telling off a wild boar. —Elena Clavarino