These Parkinsons seem to have a remarkable talent for lawmaking.
First there was the great C. Northcote Parkinson, who gave us the law that will forever bear his name, and which holds as true today as when he coined it 70 years ago: 'Work expands so as to fill the time available for its completion.'
Now along comes Michael, the veteran broadcaster, who introduced the world this week to a new Parkinson's Law of his own creation: 'If you didn't live in that time, you're not allowed an opinion.'
I shall call this one Parky's Law, to avoid confusion.
For those who missed the story of the battle of Helen Mirren's boobs, it began way back in 1975, when our Parky interviewed the then up-and-coming young actress on his TV show.
It has resurfaced intermittently ever since, with the now Dame Helen still bitterly accusing the now Sir Michael of sexism - an allegation he hotly contests to this day.
I hesitate to record her actual words about the encounter, confided to a newspaper many years afterwards.
But in the interest of letting readers gauge the full force of her fury, I feel I must (though the more shockable among you should skip the next sentence).
'I was so young and inexperienced,' she said, 'and he was such a f****** sexist old fart.'
I should say at once that any modern jury watching a recording of that 40-year-old show would have no hesitation in finding Sir Michael guilty as charged.
When I saw it on YouTube yesterday, even I found myself squirming with embarrassment and chivalrous indignation on Dame Helen's behalf - and I pride myself on being about as politically incorrect as they come.
It began toe-curlingly enough with Parky, then 40, introducing the young actress as the 'sex queen' of the Royal Shakespeare Company and saying she had won the 'ultimate accolade' of being described as 'projecting sluttish eroticism'.
If anything, it got worse.
Sir Michael went on to inform Dame Helen that she was 'in quotes, a "serious actress" ', before asking her: 'Do you find that what can best be described as your equipment hinders you perhaps in that pursuit?'
The actress - sorry, actor (I must remember it's 2016) - fought back magnificently, pressing her tormentor to admit that by her equipment, he meant her figure.
'Serious actresses can't have big bosoms, is that what you mean?' she said, bristling with anger.
Game, set and match to her, I thought.
How insulting and sleazy of Parky to tell any woman that her breasts can 'best be described' as her 'equipment'.
How doubly rude, patronising and silly to suggest to the young star of the RSC - even then a consummate actor, whatever anyone may have thought of her politics - that it was impossible for an attractive woman to be taken seriously in her profession.
But then those were my reflections when I saw it yesterday, from the perspective of the 21st century, with my sensibilities inevitably influenced by decades of exposure to modern ideas of what is and is not acceptable.
I wonder what I thought when I saw it in 1975 - as I almost certainly did, though I've long forgotten.
I have a horrible feeling I would have been firmly on Sir Michael's side, dismissing Dame Helen as an over-sensitive, mouthy luvvie, with too much self-regard to realise that he meant no harm. Couldn't she see he was only trying to flirt?
In this respect, at least, I reckon the champions of political correctness - hectoring, boring and over-the-top though they so often are - have done us all a service over the past four decades.
They've taught many of us a much-needed lesson in common courtesy and respect for others, whatever their sex, age, religion or ethnic background.
Times and attitudes change - sometimes (though far from always) for the better.
Of course, this is where Parky's Law comes in. I must say that as he phrased it - 'if you didn't live in that time, you're not allowed an opinion' - my first thought was: 'If people start enforcing this rule, I'm going to find it harder than ever to think of anything to write about in my column each week.'
For a start, I would be banned from opining that Hitler was evil, on the grounds that I wasn't alive in the days of Nazi Germany.
Nor would I be allowed to say that the Glorious Revolution of 1688, which established Britain's constitutional monarchy, was indeed glorious, while the French Revolution was an abomination.
Under a strict interpretation of Parky's Law, I suppose I would be free to comment on Sir Winston Churchill's second administration, since he was Prime Minister when I was born at the tail end of 1953.
His wartime record, however, would be strictly off limits for all those of us who entered the world after 1945.
But I'm being facetious, and I know this was not what Sir Michael meant.
If I may take the liberty of rephrasing his law, the point he was making was clearly this: 'Don't judge the past by the standards of the present.'
And there, surely, he has a good point.
For the truth is that by the standards of the mid-Seventies, much as we may gasp at them today, Parky said nothing in that interview that would have been widely regarded as unacceptable.
Indeed, Dame Helen was in the vanguard of militant feminism and her attitude had yet to catch on with the population at large.
Yes, there were some who would have thought his remarks off-colour.
But the great majority, I suspect, would have readily accepted the explanation that he offers today: 'Am I sexist? No, I'm Yorkshire.'
This was an age, after all, in which few turned a hair at a line in the popular BBC sitcom, The Likely Lads, which would drive the regulators into meltdown today.
I'm thinking of the episode in which Bob told Terry girls grew up so quickly these days that he found himself more turned on by contestants on the school quiz show Top Of The Form than by dancers on Top Of The Pops.
There's enough fodder in that one 'joke', surely, to keep Professor Alexis Jay's child abuse inquiry chewing away for weeks (if it ever gets started in earnest).
The truth is that it's just bad history to view people's past conduct through the prism of the prevailing attitudes of the present day.
I absolve Dame Helen of this charge, since she was furious at the time.
But for the most part those who apply modern standards to historic characters and events do it merely to feel smug about themselves.
I bet that nine times out of ten, they would have behaved exactly like the people they condemn, had they been around at the time.
Take the Easter Rising of 1916, of which we've heard so much in this centenary year.
I've lost count of the number of wise-after-the-event programmes I've seen, saying the British authorities were contemptibly stupid to execute the rebel leaders, thereby turning them into martyrs and recruiting support for their previously unpopular cause.
But look at it in the context of the time, when World War I was raging in France, the rebels were sucking up to the German enemy and the lawful punishment for murder and treason was death. What else could the authorities do but execute them?
Wouldn't all those self-righteous, know-it-all historians have done precisely the same?
Or take the modern fashion for politicians to apologise for Britain's conduct in the distant past - whether the slave trade or the Irish potato famine - or to dish out pardons, often posthumously, to people found guilty of behaviour that is either no longer a crime or is looked on more kindly these days.
I can see it may have given David Cameron a warm glow of self-satisfaction when he secured a Royal Pardon for Alan Turing, the gay code-breaking genius who made such a colossal contribution to our victory in World War II.
But a fat lot of good it will do the long-dead Turing.
Nor can it alter the fact that when he was convicted of gross indecency in 1952, homosexual intercourse was a crime - however cruel and wrong we may now think the old law.
The same goes for Tony Blair's blanket pardon for 306 deserters shot for cowardice in World War I.
Yes, some brave men were wrongly convicted.
But others were cowards - and the penalty for desertion was death.
We surely gain nothing by trying to muck about with history.
Am I being too blunt and antediluvian?
Put the explanation down to the geographical origins of the Utley family.
Like the creator of Parky's Law, we're Yorkshire.