Queen Elizabeth II, who has been on the throne for 64 years, turns 90 today.
Her life to date has spanned an almost indescribable period in human history.
The monarch was born eight years after the end of the Great War horror, was in her teens when the disastrous Second World War began, and an adult when it ended.
Britain was still the pre-eminent global empire in 1945 but within a few years that position had collapsed.
The post-war UK was a society that fast changed beyond recognition, with universal healthcare and welfare provision and rapid strides in equality for women. TV was almost unknown in the late 1940s and now it is almost old technology.
A social revolution that began with sex and drugs and rock ‘n’ roll in the 1960s is now heading towards things such as same-sex marriage.
Here in Northern Ireland we were plunged into a Troubles at the end of the 1960s that few observers foresaw and that took the best part of 30 years to bring largely to an end.
Through all this upheaval, and at times turmoil, the Queen has been either directly in line to the throne, or on it, and always a reliable, unchanging and steadying figure.
She is viewed with respect, and even awe, around much of the world for the dignity and circumspection with which she has fulfilled a role that she clearly sees as a God-given duty, as is apparent in her increasingly religious pronouncements.
This helps to explain how, as the monarch has approached her 90th birthday, both she and the Duke of Edinburgh (who sailed past his own 90th birthday almost five years ago) continue to fulfil a rota of engagements that would exhaust people half their age.
Those engagements are gradually getting fewer in number as the inevitable passage of time takes its toll. No-one will resent that. We are as a nation fortunate to have had such a head of state for so long. The outpouring of affection for the Queen on this birthday is testimony to the public recognition of that.