Can you imagine anything more terrifying, be you male or female, than suddenly awakening to find a man you have never seen before in all your puff leering over your bed?

Carrying a piece of broken crystal ashtray; blood dripping from his fingers? Your partner in life, meanwhile, sleeping in another room and beyond earshot, because he has an early start in the morning?

It would prove, when all was made well, the only occasion when this doughty woman, 56, ever swore. But, first, our lady – let us call her Elizabeth – had in cold, swift courage to dial things down.

She pressed an alarm button by her bedside. Meanwhile, she engaged in conversation with this oaf.

There was no response to the alarm. Elizabeth then picked up the bedside telephone and, in as low and neutral a tone as possible, asked for the immediate attendance of a policeman. Perhaps too calmly: the bored chap taking the call detected no urgency, and responded with none.

The day was saved when the maid turned up with the morning cuppa, hailed what she saw with one expletive, put the trayed Earl Grey down quietly, and scampered to recruit a very tall 23-year-old footman Her Majesty scarcely knew.

He managed to lure the intruder aside for cigarettes as, an age later, the Metropolitan’s finest finally lumbered up the stairs. The first PC Plod, espying Elizabeth, promptly pausing, awkwardly, to adjust his tie…

‘Get a bloody move on,’ roared our late Queen, after an eternity wondering whether she was just about to be set upon.

It was not in the least bit funny, heads appropriately rolled, the blameless Home Secretary offered his resignation – and old hands at the Palace for decades thereafter shuddered.

In not two years preceding Michael Fagan’s intrusion, the Pope and the President of the United States had both been gravely wounded by would-be assassins – and John Lennon and Egypt’s President Sadat had been murdered.

Do you cuss and swear? I try not to. In fact, I don’t, and never have, save for scant and very silly years in my early thirties when I went through a bit of oh-how-I-pity me and propped up a couple of Hebridean bars.

The simplest explanation for this is that my parents – as one would expect of a stately couple who, over the decades, adorned this or that Free Church manse – never used bad language.

The strongest epithet in my late father’s vocabulary was the endearing, ‘Dear Donald’ – and the first rule in raising children is always to remember that monkey see, monkey do.

I was also schooled in an era, from 1971 to 1984, when you simply did not hear such language in the public square.

A host of epithets were deemed unbroadcastable, I cannot recall any politician of that era who effed and blinded and – with one exception, an endearing but hapless deputy headmaster – I never heard a teacher curse.

We were still just in an era where there was a vague folk memory of the monastic roots of education – staff in black gowns; the school day launched with morning prayers – and, accordingly, regard for at least the veneer of decency.

One household name broadcaster, Bill Grundy, was in 1976 ignominiously sacked after he invited the Sex Pistols to drop the F-bomb live on telly; and the Duke of Edinburgh’s frequent salty turn of phrase invited much tut- tutting in the papers.

A bit rich as, even then, there was no swearier environment than a newsroom – all the more disconcerting when you were told at every turn that educated people from decent homes simply did not talk like this.

And here we are today – washed up in a era when the President of the United States threatens to obliterate a civilisation, his rhetoric larded with obscenities; when the script of crisis engulfing our Prime Minister is fat with the F-word; when insider accounts of the corridors of power portray a world of cursing, vituperation and the foulest Anglo-Saxon.

Glancing at accounts from the likes of Andrew Rawnsley or Tim Shipman, it defiled the Downing Street days of Tony Blair, Gordon Brown and even Theresa May, whose principal consiglieri, Nick Timothy and Fiona Hill, were noted not just for their extraordinary rudeness even to Cabinet ministers but for their dreadful language, sometimes in Mrs May’s very hearing – till the disastrous 2017 general election, for which the pair had eagerly pressed, put an end to their brilliant ideas.

Then the salons of No 10 soon resounded to the refrains of Dominic Cummings.

From whence has this ghastly modern culture sprung? Partly the general collapse of, at least, pro forma Christian observance.

The silent death of untold taboos – there used to be a host of things which people simply did not discuss in public – and that we are in an increasingly digital age.

Emails, text messages, social media, the blogosphere and so on: a realm where folk with impunity can vent their inner Malcolm Tucker and, sadly, too often do.

Especially in formats such as certain reality TV platforms – yes, Gordon Ramsay, I’m looking at you – that seem to exult in it.

Which is not to suggest that our great-grandparents were naïve innocents.

The late Queen Mother was once, at some occasion, in the company of Noël Coward as they ascended a stair lined with extraordinarily handsome soldiers – and noted the playwright’s lingering regard.

‘I wouldn’t if I were you, Noël,’ she murmured, amused. ‘They count them before they put them out…’

Few, even decades thence, ever dared to ask Elizabeth II about that terrifying morning in 1982. Those who did seldom got past one line at once laconic and forbidding, ‘You seem to forget that I spend most of my time conversing with strangers.’

But, in lighter off-duty moments at Balmoral and so on, she could peerlessly mimic that lass who had fatefully brought in the tea – ‘Bloody ‘ell, Ma’am, ‘e shouldn’t be here!’

The lofty footman who had saved all, Paul Whybrew, became her most trusted male retainer.

For years the honoured Page of the Backstairs and, from 2008, her official Serjeant-At Arms.

‘Tall Paul’ would feature in that James Bond skit at the 2012 London Olympics and at the last march behind Elizabeth II’s coffin.

Decades before, on the eve of the landmark 1991 State visit of the new President of Poland, the Queen side-eyed an aide. ‘They say Mr Walesa knows only two English words.’

And tilted her head.

‘I believe they are rather interesting words.’