Robert Devereux, the 2nd Earl of Essex, was a sulky, spoilt brat, given to tantrums and threats to get his way. Despite that, as her favourite at court, he was much indulged by Queen Elizabeth I.
Perhaps for Essex it was unfortunate that Elizabeth was childless, for any parent knows that tolerating such behaviour only leads to more of the same. Not unpredictably then, in one of his periodic fits of pique, Essex finally overstepped the mark. He began plotting to depose Elizabeth and to put James VI of Scotland on the English throne.
Queen's favourite or no, when the plot was uncovered she didn't hesitate in signing his death warrant. In Elizabeth's eyes, Essex had committed the unforgivable sin of "reaching for the sceptre". Putting up with his childish behaviour was one thing, but when he began to threaten her position it became quite another.
The changed relationship between the Irish Government and Sinn Féin isn't entirely analogous - no one is likely to be beheaded, for a start - but there are similarities.
While they posed no real electoral threat, Sinn Féin's tantrums and demands were largely indulged. The Government didn't dwell too much on republican bad behaviour, preferring to ignore the nature and extent of Sinn Féin's relationship with the IRA and the evidence of that organisation's many and varied anti-democratic activities.
Like the favourite at court, Sinn Féin merely had an occasional, but indulgent, shaking of the government head to contend with.
Now, with recent opinion polls showing Gerry Adams to be the most popular party leader in the Republic and Sinn Féin looking certain to make further electoral inroads, things have dramatically changed. The republican movement suddenly looks capable of threatening the Government's position.
And, as the Sinn Féin hand has moved closer to the sceptre, the days of indulgence have been brought quickly to an end.
In fairness, concern at Sinn Féin's growing popularity in the Republic is based on more than narrow party political interests and extends beyond political circles. If Sinn Féin were a normal political party, it would hardly matter. But, of course, it isn't; it comes complete with an illegal army. And one that has shown no indication of a willingness to depart the stage.
The anomalies inherent in this quasi-political organisation being granted, of necessity I believe, executive positions in Northern Ireland may yet prove impossible to overcome. Yet the Northern Ireland Assembly has only limited powers devolved to it, with the insurance policy of ultimate sovereignty lying at Westminster.
The anomalous implications of Sinn Féin, in its current form, being able to command a similar role in the governance of an independent sovereign state like the Republic, complete as it is with its own military and policing apparatus, are far more serious.
Unlike Northern Ireland, the Republic has no insurance policy to fall back on. Whether or not its political and social characteristics remain liberal and democratic depends entirely on the good sense or otherwise of its electorate.
Against that backdrop, when a political party complete with its own private army/criminal organisation begins to look capable of being elected to sovereign governance, democrats have every right to be worried.
The Minister for Justice, Michael McDowell, when he likened the republican movement to the Nazis, was warning against a naive belief that executive power somehow puts a brake on anti-democratic tendencies. As Germany and everyone else learnt to their cost after January 30th, 1933, power tends to further corrupt the already corrupted.
In Northern Ireland decades of IRA violence had created a discernible ceiling beyond which, in the absence of a prolonged IRA ceasefire, electoral support for Sinn Féin would not go. There is no way that the potential for Sinn Féin growth in the Republic can be gauged with anything like the same degree of accuracy.
It is hardly likely that Bertie Ahern believed his public ruminations on Gerry Adams's exact position within the republican movement, or his drawing of attention to the IRA's ongoing criminal activity, would cut much ice with the disaffected communities from whom Sinn Féin traditionally draws its support.
Nor, I imagine, did McDowell think the same voters would be too concerned about the possible constitutional ramifications of Sinn Féin being returned to the Dáil with a far larger political mandate. They know that the whiff of cordite and an opportunity to hit back at the establishment is more likely to attract than repel those who feel they have been abandoned on the margins of a prosperous society.
It seems, therefore, that Ahern and McDowell were aiming their remarks at a much broader audience than that. So, wherever the ceiling to Sinn Féin support in the Republic currently sits, it's clear the Government now feels it to be some way above merely the disaffected and disillusioned. If that is indeed the case, they have good reason to be concerned about that hand inching ever closer to the sceptre, and are duty-bound to point out the inherent dangers to the electorate.