Why be a monarchist? As the country enters eight days of official mourning following the death of Prince Philip, it is a fitting time for those of us who support the institution of which he has been a pillar for so long to reflect on our reasons.

The Duke of Edinburgh’s passing is a sad reminder, as Andrew Gimson wrote yesterday, of the mortality of the Sovereign. And since the popularity of the principle of monarchy tends to under-poll the popularity of the monarch – especially one so universally admired as Queen Elizabeth – a reminder that its current hold on public affection cannot be taken for granted.

We might need to make our case, perhaps sooner than anybody wishes to imagine. So we had best prepare it.

So why royalty? There are different answers. Matt Kilcoyne talks about the value of having as the central drama of the nation a family story, told across several generations, rather than the presidential cycle of heroic but transient figures and interminable origin stories. Writing in 2012, Sunder Katwala made a pitch that the left should reconcile itself to the monarchy that put Prince Philip front and centre:

“We don’t even think of the Queen as having married an immigrant, so well integrated into British life has her Greek-Danish prince become. Prince Philip enjoys broad popularity, running neck-and-neck with Trevor McDonald ahead of sports and pop stars in an Ipsos MORI poll asking which foreign-born figure has made the biggest positive contribution to Britain.”

There is also much to be said for having a head of state who can be a non-partisan focus of pageantry. Coronations and jubilees allow the country to come together for events that don’t celebrate the triumph of one party, faction, or tribe.

The long history of the monarchy provides context and legitimacy to national rituals. George Orwell, another left-winger with a better grasp on this stuff than most of his comrades, put it best in his defence of anachronism in The Lion and the Unicorn:

“It is continuous, it stretches into the future and the past, there is something in it that persists as a living creature. What can the England of 1940 have in common with the England of 1840? But then, what have you in common with the child of five whose photograph your mother keeps on the mantelpiece? Nothing, except that you happen to be the same person. Above all it is your civilisation. It is you.”

A republic would need new ceremonies and honours, if its self-consciously modern advocates could even recognise the value of them, and they would inescapably be shallower than those they replaced. No epic struggle against tyrants to sanctify a British republic, just a technocratic tidying-up exercise and likely the symbols to match it.

Meanwhile for constitutional conservatives, the monarchy plays vital role in the evolved elegance of the British constitution. The Crown is a vessel in which substantial powers can be safely vested, precisely because the Queen does not herself exercise them. Instead, the Royal Prerogative provides a perfectly normal suite of executive powers (obvious at least to those who can see past the word ‘royal’ in the name, which isn’t everyone) that can be wielded by a Government that sits in, and is directly accountable to, the elected House of Commons.

As with the House of Lords, there is no credible case for a presidency which rests on the position being essentially ‘the same, but elected’. Mandates have their own force and institutions a life of their own. Either a president would end up attempting to wield these powers, or they would have to be stripped from the head of state and found a new home.

The abolition of the monarchy would, therefore, almost certainly entail much broader constitutional reform, delivered by the sort of people responsible for such triumphs as the Supreme Court, devolution, and the Fixed-term Parliaments Act. God save the Queen.