The Queen’s fragile smile in the official photograph released as she waited to appoint Liz Truss as her 15th Prime Minister carries even more meaning now. Her Majesty clearly knew there would be no 16th and after a turbulent summer it must have come as a relief to know that the country was about to move from a caretaker premier to a full-time one. Her audience with Ms Truss would prove to be the last significant act of a monumental reign lasting 70 years. And it meant that in her final days she could look back on the improbable promise she gave her future subjects on the occasion of her 21st birthday in 1947 and know she had fulfilled it in every respect.

‘I declare before you all that my whole life whether it be long or short shall be devoted to your service,’ she had said, never imagining that just five years later she would take over as monarch and reign for seven decades.

News of her death is a shock but it should not come as a surprise. At 96 and in obviously fading health for some time, it was a moment most of us knew would come soon. But it still lands as a profoundly shocking hammer blow to our collective morale in the midst of already tough times for the United Kingdom.

The idea of a person being a ‘rock’ in the life of others is somewhat overused. For a fleeting period, Princess Diana allegedly regarded one of her butlers as such. But the Queen really was such a thing to many millions of Britons – self-disciplined and self-denying to an extraordinary extent in an era when opinion-sharing became a shallow cult that swept-up other members of the Royal Family.

The image which best captured the tenor of her reign, above all others, is surely the relatively recent one of her sitting alone at the funeral of the Duke of Edinburgh during the Covid pandemic. Few would have chided her for bending the draconian rules in place at the time and having at least one close family member beside her to hold her hand and provide comfort. But she was determined to put duty first and share fully in the privations of her subjects even at such a distressing moment.

As stories later tumbled out about the slapdash approach to lockdown of her then prime minister, Boris Johnson – reports that destroyed the faith many people had in him – the remarkable wisdom and strength of Queen Elizabeth II became even more apparent.

When the Commons debate on energy policy – the first big headline debate between Truss and Keir Starmer – was briefly interrupted on Thursday for a grim update about the Queen’s condition to be shared between the frontbenches, the looks of shock and sorrow on both sides were unmistakeable.

For the first time, the UK has both a prime minister and a leader of the opposition who openly espoused republicanism as young radicals. Yet there is little reason to doubt that both now sincerely see the error of their ways and that it is the greatness of Elizabeth II that changed their minds.

Even as Truss and Starmer shared in the nation’s grief they will have been thinking about the impact such a profoundly sad moment will have on their respective political fortunes. This is not because they are unusually cynical people, but because that is the unrelenting nature of politics.

The sheer extent of public sorrow will dominate national discourse for weeks to come, not merely in the media or among the great and the good, but in countless millions of conversations wherever people gather to talk.

At times like this, prime ministers are expected to step up and speak for the whole nation. If Truss manages to put on a sure-footed display in the days ahead she will certainly grow in stature in the public eye. Starmer, for his part, will wish to register that he is a fitting and sufficiently dignified person to be entrusted with great affairs of state.

King Charles III, of whose political thoughts we all know far too much, faces an even bigger challenge. To say his mother is a hard act to follow qualifies as one of the great understatements. But he must now show he can at least keep his trap shut in public – apart from when reading out scripts written by his ministers – and confine his opinionated utterances to gentle asides in private audiences with them. We must not let daylight in upon the magic, exhorted Walter Bagehot. The constitutional stability of the UK rests on him adopting that mantra now.

When Queen Victoria stepped back from public life for a protracted period to mourn the passing of Prince Albert many of her subjects came to regard it as an indulgence and were unable to share in her grief for long. Elizabeth II did not allow herself such an extended seclusion upon the loss of Prince Phillip, so focused was she on duty and the realm.

But when it comes to her own passing, a profound sense of sorrow and loss will be far more widely shared. The only person of the modern age who could be regarded as the greatest Briton ever to have lived is gone and that will take quite some getting over.

At the weekend a newspaper political correspondent, who meant no offence and shall remain nameless, ventured that the imminent appointment of Liz Truss as PM would mean ‘a new Elizabethan age will begin’. It won’t. Compared to the woman we have lost, prime ministers are ten-a-penny politicians: here today, gone tomorrow as Robin Day once put it.

We were all Elizabethans already and now we are not.