One recent afternoon, in the pay & display car park next to my favourite book shop, I was merrily depositing surplus 5-pence pieces in the ticket machine, feeling more and more pleased with myself the closer I got to my fifty pence target. We can all relate to the disproportionate relief of purging a purse or wallet of those low-value coins that you never get around to spending in the corner shop because, being British, you have a horror of being tutted at or, more woundingly still, eyerolled by your fellow citizens in the queue.

I was a tantalizing fivepence away from the prize of a parking ticket when the machine, like an unwilling toddler at dinnertime, simply refused to swallow a penny more. I kept offering it alternative, tastier 5p’s, but it was having none of it and, in the end, vomited the whole lot back out at me, triumphantly declaring the transaction cancelled (machine-speak for “now naff off”).

Aware that somebody was waiting behind me, I stepped back and invited him to chance his luck with the mulish contraption. Needless to say, it was the very model of compliance with him. Being a kindly-looking Brummie sort, and of course ignorant of the fact that I only required fifty pence-worth of parking, he then turned to me and said, “Here, would you like to swap two 50p’s for a pound coin and try that?”

Well, that stumped me.

Gazing into my purse that was positively portly with one-pound coins, and thinking to myself “But I only want 50p’s worth of parking,” I heard myself saying “Oh, yes, thank you very much.”

I fumbled in my purse for two of my three 50p’s, ignoring the beseeching voice in my head that was murmuring “But you like 50p’s, they’re hexagonal,” and trying to conceal the dragon’s hoard of pound coins that already lurked within. Having concluded the vestigial swap, I said another thank you for good measure, and shuffled back over to the ticket machine – which, I could have sworn, was now smirking at me.

At this point, I was struck by a further dilemma: I had to feed my remaining 50p into the smug little git of a machine without my Car Park Messiah of the Midlands seeing me do so because a) he would wonder why I wasn’t availing myself of his superior pound coin, and b) he would then conclude that I am a bit strange.

Hunched furtively over my still dismayingly heavy purse, I secreted my last 50-pence piece in my palm and swiftly slipped it into the slot. Hallelujah! There was the kerplunk of an accepted coin. I jabbed the green button before the accursed machine could realize its folly, snatched my parking ticket, and scurried (hobbled, actually, as I have a decrepit ankle) back to my car, trailing what I thought must surely be a visible cloak of confused shame in my wake.

This is not the first time I have pitched head-first into a pothole of utterly pointless politeness. Exactly how deranged did I think this guy would become if I were to decline his pound coin substitution on the grounds of ACTUALLY ONLY NEEDING FIFTY PENCE-WORTH OF PARKING?

Apart from my Britishness, I have no explanation for my ludicrous leaning towards misplaced gratitude and good manners. Except – I’m oddly slow-witted when it comes to impromptu interactions. There’s something about being confronted with Real-Live-Strangers that wrongfoots me. An almost simpering desire not to cause the remotest offence kicks in and, more often than not, I end up looking, or at least feeling like, an utter eejit.

Though I can laugh it off as one of my quirks, I do get frustrated with my very peculiar politeness. If I can’t even say no to a coin exchange in a car park, how can I ever assert myself in matters of actual importance? I’m not what you might call a meek individual: I can be exceedingly stroppy when the mood so takes me, and I am capable of the whole polite-but-firm thing – provided I can politely but firmly state my case in an e-mail, rather than to an actual person with a face and everything. I possess a good deal more pluck in writing. Spontaneous self-assertion, in even the most trivial situation, eludes me.

I suspect that, Britishness aside, the reasons are threefold: I was raised by a father who would concoct ever-more elaborate white lies in order to evade social engagements without causing offence to anyone; I am a self-conscious introvert; and I am, indeed, a bit of an eejit.

Oh well. No matter. I’m off to the corner shop now to buy some Farmer Jack’s Garlic Bread Slices. They cost £1 exactly, and I want to start getting rid of some pound coins…