On Wednesday, Governor-General David Johnston committed a small, barely noticeable breach of royal protocol: At a Canada 150 event in Britain, the man whose job it is to represent the monarch reached out his arm and held her elbow as she descended a staircase.

Out of respect, you're not supposed to touch the Queen, but the impulse behind Mr. Johnston's move was easy to understand. The woman who has been on the throne for 65 years, and who is on her 12th Canadian prime minister, is still in remarkably good health. But she's 91 years old.

The old song may wish that she will be "long to reign over us," but the longest-serving sovereign doesn't have many years of reigning left. Someday, she will pass.

Story continues below advertisement

When that happens, some Canadians will say this country should use the opportunity to redesign the institution of the head of state. Get rid of the monarchy and replace it with a fully-empowered governor-general, maybe even an elected one, thereby repatriating the last element of Canada's constitutional order.

What do we think of that idea? We think it would be a huge mistake. Our unique constitutional monarchy, the product of 150 years of thought, compromise and accident, is a fluke work of genius.

Prime Minister Justin Trudeau last week designated a successor for Mr. Johnston. Astronaut, engineer and business executive Julie Payette, who has led a career filled with achievements, will surely make a superb occupant of the office. She was no doubt selected because she represents Canadian excellence, and also because, as a Quebecker and a woman of tremendous accomplishment in science and technology, she represents things the government of the day wants to be associated with.

But Ms. Payette will also represent something else: A monarch who doesn't live here. And that is a part of what's so smart about the Canadian system.

Constitutional monarchy is arguably the best form of government going, practiced by some of the world's most successful and admired societies, from Norway to the Netherlands and Sweden to Japan. But Canada has produced an innovation to constitutional monarchy that makes our system just a little bit better.

Ms. Payette will fulfill the duties of a head of state – but she won't be a head of state. Like Mr. Johnston and governors-general before her, she will be merely a viceregal representative. She'll be standing in for somebody else, permanently. It's a humbling arrangement – never a bad thing when it comes to politics and power.

If constitutional monarchy is monarchy-lite, Canadian constitutional monarchy is monarchy-lite, plus monarch extra-lite.

Story continues below advertisement

The monarchy is the bedrock of Canada's constitutional order. If you commit a crime, you will be prosecuted by the Crown in the name of the Queen. In Parliament, a bill isn't a law until it receives royal assent.

The Canadian innovation has been to keep monarchy, while turning a non-resident monarch into less of a physical presence and more of an abstraction. And abstract ideas can be more powerful, durable and flexible than physical things.

Some of the Fathers of Confederation, including Sir John A. Macdonald, wanted to call this country The Kingdom of Canada. The Kingdom of Canada might eventually have emulated many newly independent European countries of the late 19th- and early 20th- centuries, importing a suitable member of the British Royal Family, and making him or her our local, resident, hereditary King or Queen of Canada.

It's a very good thing that did not happen. Instead, we have the institutions of monarchy, but without a resident monarch. It gives us a living constitutional monarchy, but with a figurehead who is to a large extent notional and virtual.

That turns Canadian governors-general and provincial lieutenant-governors into permanent second fiddles to a first fiddle who is never around. It also makes them seem kind of boring, which is fine, seeing as the monarch's representative has an actual job, and it isn't to sell more copies of Hello! magazine. Nor is it to be Canada's version of the Royal Family – which in Britain is the nexus for an entire industry of tabloid journalism and reality TV.

Earlier this summer, British Columbia's Lieutenant-Governor, Judith Guichon, was asked to do that rarest of constitutional jobs. She had to ensure that her province had a government. And after an election that delivered a hung parliament, she had to decide whether a government could be formed, or whether new elections were needed.

Story continues below advertisement

If something like this had happened in the U.S., it would have involved slow, painful and divisive litigation. In Canada, however, the question was kept out of that sphere, with the Lieutenant-Governor relying on convention.

Eureka, the Canadian system works.