The Queen's 90th birthday week has produced a mixture of deferential reporting and, as can be expected for someone approaching a century, an opportunity to think about the times that she's reigned through - our current Elizabethan Age, as the cliché goes.
For me, the most powerful stimulus for this kind of thinking was the publication of the official 'Four Royal Generations' photograph. The picture shows Prince Charles, the Queen and Prince William seated, all smiling at the camera with young Prince George standing on a pile of books between the Queen and William.
My immediate association was to the other Four Royal Generations photograph of 120 years ago. A seated Queen Victoria gazes down at her great-grandson, the new royal baby. Behind Victoria stands her grandson (the future George V) and her son (Edward VII). The baby cradled in her arms was of course to become Edward VIII (or Duke of Windsor).
Perhaps more striking than the similarity between the two pictures - the formal composition, the gender distribution down the generations, the attempt by a royal family to present an image of continuity, the rarity - is the lack of any reference to the older photograph in this week's reporting. Across the board - newspapers, TV, radio, Twitter, there's no mention of it. What could explain this?
We may not know, but two factors come to mind. First, our collective memory seems to have got shorter and shorter. We don't seem to know or remember our past. Second, for those who do know the history, it's a case of the elephant in the room.
Start comparing the two images, and you end up comparing the individuals. Substitute Victoria for Elizabeth II, Edward VII for Charles, George V for William and err, the Duke of Windsor for George.
The main PR embarrassment of course, relates to the less desirable traits of the 1890s royal family - Edward VII and his mistresses, George V and his passion for stamp collecting, not to mention the purported political sympathies of Edward VIII. Readers will no doubt make their own judgements about the individuals in the 2016 picture.
Individual comparisons aside, the similarities between the two eras are uncanny. At first glance, the 1890s picture portrays a certainty about Britain's place in the world which contrasts unnervingly with our situation today. Queen Victoria exuded confidence as head of an empire which still had a quarter of a century's expansion to go. Not that similar to our current financial and political jitters, you may think. Little did the royals in the picture know however, that the country was close to the Boer War, or even start to imagine the horrors of World War I.
The youngest in the earlier photograph - Edward VIII died in May 1972, four months after the UK signed the Treaty of Accession to join the European Community. This week's photograph has the spectre the EU membership referendum looming over it.
Royal portraits are meant to ensure stability and continuity. But the people in the original picture were soon to look east. A couple of decades later, George V and his two cousins - the Kaiser and Tsar were the leading monarchs in Europe, their countries fighting a bitter war. George was to make the callous (or wise, depending on perspective) decision to decline the Tsar and his family refuge in the UK.
As for 2016, even the eldest individual in the photograph might reign through the disintegration of the UK as we know it - leaving us with an independent Scotland and a sort of 'rUK' ('rest of the United Kingdom'). The youngest could be expected to see in the turn of the 22nd century. Barring a major shift in public opinion, the UK is still not likely to have an elected Head of State by then. But further afield, Commonwealth nations bowing to UK royalty are likely to disappear like candles blown out on the Queen's birthday cake.