YOU could tell instantly by the tone of Judy Murray’s tweet that her visit to the doughnut shop in London had been a double outrage.

First there was the matter of the £9 price tag for two – TWO! – doughnuts. The tennis coach and mother of Wimbledon champs Andy and Jamie Murray must already have been regretting the decision not to go to Greggs for her sugar fix when she handed over her Bank of Scotland tenner only to be told by the cashier that the shop accepted only “British” notes.

Read more: Judy Murray's Scottish banknote refused in London bakery

As anyone who has read Ms Murray’s excellent book outlining how she set her sons on the road to sporting greatness through sheer determination will know, Judy is not a woman who takes no for an answer. And, as her quarter of a million Twitter followers will attest, only tennis ranks above her love of cakes. So, although she didn’t elaborate on the outcome of the altercation, I can only imagine Ms Murray volleyed back as good as she got and ended up persuading the shop to accept Euros, groats and Monopoly money as well as Scottish cash.

The tweet got so much traction because most Scots know and understand exactly how this interaction goes, just how grim and maddening it is no matter how many times you’ve experienced it. These days many of us feel much more confident in our skins as Scots and are able to consider and reconcile our relationship with our English neighbours in more mature and expansive ways than ever before. But you still can’t escape the deep, primeval humiliation of having your money refused. And although this refusing is often down to ignorance rather than malice, especially in London, where so many of those who work in shops, restaurants and cafes are from overseas and don’t even know what a Scottish note is – why would they? - it’s something we Scots just can’t seem to get over. I include myself in this. I’ve lived in London twice and looking back I used Scottish notes to symbolise and conflate the many different frustrations I felt with life in the metropolis.

Read more: Why Scottish banknotes can be rejected

I could have given Basil Fawlty a run for his money as I pontificated to teenage shop assistants and foreign taxi drivers about “legal tender” and “anti-Scottish discrimination”, eventually admitting to myself that I found the ranting enjoyable, a form of stress relief, regardless of whether I succeeded in forcing my money upon them or not.

I’m ashamed to admit now that I used to keep a Scottish tenner specifically for the purpose of having a good rammy with the landlord of one of my local pubs. I suspect he enjoyed it just as much as I did, not least because he’d never miss an opportunity to bring up the old cliché about Scots being tight. To give him his due, I’d usually get a wink and a free drink, too.

The irony of all this, of course, is the fact that the banknotes so many of us defend to the end at cash desks all over England, day in, day out, are not legal tender at all. Not even in Scotland, as it turns out, where only coins have legal weight. According to the Bank of England, both coins and Bank of England notes are legal tender south of the border, with anything else a “matter of agreement between the parties involved”. This means each and every one of those painful refusals was legitimate, every “put that in your pipe and smoke it, pal” righteous speech made by you was nonsense. I found this out during my second stint in London, changing tack from rants around legality to arguments based on how petty and “hurtful” (flash sad eyes) their actions were. I had more luck with that.

Read more: Judy Murray's Scottish banknote refused in London bakery

Former Lib Dem Scottish Secretary Alistair Carmichael - remember him? - apprently plans to introduce a bill to the House of Commons that would oblige businesses to accept Scottish banknotes as payment. The current incumbent in the job, David Mundell, tried and failed to do something similar in 2009.

Other than the fact Parliament probably has more pressing concerns right now, surely this is simply a case of too little too late? With most of us using debit cards and contactless payments these days – only three in 10 transaction now use notes and coins, a figure expected to halve over the next decade - it’s clear the days of carrying banknotes of any sort are numbered: the cashless society is within swiping distance. Sweden, the first country to use the banknote back in 1661, is expected to be the first to go completely cashless in 2023.

Read more: Why Scottish banknotes can be rejected

Maybe the time has finally come for Scots to stop fighting the good fight? Next time someone refuses your Scottish note, remain Zenlike. “How could I have been so silly?” you will smile as you bring out your contactless card, resisting the urge to scream “it’s legal tender, you ignoramus!”. Not as much fun, granted, but so much better for the blood pressure.