Regular readers will know that we’ve been running a campaign over the past few months to try to stop car-hire firms being sneaky so-and-sos, with their sneaky hidden charges and their sneaky adding of extras on your credit card once you’ve flown home. We were tired of all this sneaky sneakiness.

So imagine our excitement when, the other day, an announcement came from the Alamo press office entitled “Alamo and National Respond to Criticism of Rental Industry”. It promised not much — “the option to pay by debit card, two-hour reservation and two-hour holding time for cars and a new, clearer rental wallet”. But at least they’re trying.

Trouble is, a few days before that, I’d hired a car through Alamo’s Dublin office. And I had set myself a challenge: I’d hired the car, paid a deposit and had just €56.40 to pay. And upon my life, that was all I would pay. I knew the game, I knew the sneakiness and, as a travel journalist with a dangerously geeky interest in car rental, I would resist all sneakiness and win. So I triple-checked the small print, took out my own excess-reduction policy and flew to Dublin, ready to do battle.

Tap, tap, tap, tap, tap, taps the woman at the Alamo desk.

“The excess is €900. It will cost €13 a day to reduce that.”

“No, thanks,” I counter.

“I’ve already got my own excess-reduction insurance” (so ner-ner-ne-ner-ner).

Tap, tap, tap, tap, tap, taps the woman, unimpressed. “€90.40 to pay,” she says with a sneaky flourish.

“No, no, no, no, no, it should be €56.40. Howdyugetninety?”

“Well, it’s got half a tank of petrol and you have to return it empty. That’s €28.”

“But I don’t want to bring it back empty.”

“It’s going back to the dealership. You have to bring it back empty.”

“Fine, whatever.” (I will allow her to win the fuel battle, but she shall not win the war.) “But 28 plus 56.40 makes 84.40. Wheredyugettheextrasix?”

There’s tutting in the queue behind me now. Don’t they appreciate that I’m fighting this crusade on their behalf? Tap, tap, tap, tap, tap.

“The extra is for third-party insurance, which is compulsory, and for the credit-card transaction fee — which is also compulsory.” Game, set and sneaky match, Alamo.

I leave the airport fuming, but driving sensibly and in no way damaging the vehicle in the process (that’s important for later in this tale). Drop it off a couple of days later, give the keys to the guy in the hut, ask him if everything’s okay, he says yes and I fly home.

A week later — and two days after that announcement about how Alamo are heroically responding to criticism — my credit-card bill falls through the letter box with a suspiciously heavy clunk. There’s the £63.03 (€90.40), still annoying because it should be £38.57. But below it, another £142.84 whacked on without explanation.

Resisting the temptation to walk out onto the streets with a machinegun and execute the first car-rental agent I find, I call the number at the bottom of the press release (yes, the one about how great they are) and I am promised a full investigation. An hour later, a call promising a refund. A worryingly quick capitulation.

Then, two days later, the result of the investigation: “Alamo would like to apologise to Mr Rudd for the events relating to his recent rental in Ireland... our Dublin operation did not adhere to our policies in relation to fuel and damage charges. This is being addressed as a matter of urgency to ensure it does not happen again.”

They accidentally charged me for a full tank of petrol, then accidentally charged me for damage they had accidentally forgotten to mention. “What damage?” I ask, because they’ve not been exactly forthcoming with the specifics. Apparently, I had damaged a hubcap and tyre: “It looked like it may have hit the kerb at some point.” I’m sure I didn’t, and, since there was no check for damage at the start or the end of the rental, I don’t know how they think they know I did it. The onus is on them to prove that damage occurred during the rental and not outside it (when one of their boy-racer employees — I’m making that up, but I’m angry — could have pranged it).

What if I hadn’t bothered to check my credit-card statement? Or, worse, what if I were a long-sighted pensioner, too frail to question unwarranted charges? Then I would have been a ripped-off pensioner.

Is this a one-off? Alamo says it is, but the ease with which my bill rose from £38.57 to £205.87 was shocking. As it stands, I’ve had a refund and a fulsome apology. So I’m all right, Jack, but are you? E-mail me at matt.rudd@sunday-times.co.uk if you aren’t.