By threatening Canada, Donald Trump has not only risked the US-Canadian relationship but the US-UK relationship as well, says Sir Jacob Rees-Mogg

Yet his Canadian majesty is the head of state of a country that Trump wants to annex and has hit with brutal tariffs.

I am broadly a Trump supporter; I think his robust good sense and political drive are essential. However, I am a loyal subject of my King in all his realms. Thus I support Canada in its row with the United States.

Canada is and cannot be a vassal state. It is a sovereign nation with its own traditions and history intrinsically intertwined with our own.

Remember, Canada backed us immediately in 1939 at the beginning of the Second World War, while the United States took all our money and only joined after Hitler declared war on it.

Canada fought alongside Britain in the Gulf Wars, in Bosnia and Afghanistan and Libya. It's one of our greatest allies and closest cultural partners.

Canada is a country grounded in constitutional monarchy, in parliamentary democracy and the rule of law - systems Britain helped shape and which Canada now owns entirely, proudly and independently.

When the king visits Canada, he does not go as a guest but rather as head of state of a nation that has chosen to keep the Crown, not out of obligation, but out of respect, continuity and, indeed, affection.

And this visit is truly pivotal in the future of inter-Anglo relations. The special relationship is real when the Americans want it to be.

And there is no doubt Donald Trump is enamoured by the UK because of his Scottish roots and because, like so many people, he adored the late Queen.

But he must also understand that Western allegiances ought to extend beyond our two nations.

By threatening Canada in such an incendiary manner, he has not only risked the US-Canadian relationship, but the US-UK relationship as well, not least that, with the King.

It is in moments like this that prove the efficacy of constitutional monarchy, a great symbol that unifies all above politics, a living link to history and tradition and a continuity in times of increasing uncertainty.

The good news is Donald Trump loves the British monarchy, so perhaps, just perhaps, it ought to be restored and rather than Canada becoming the 51st state the USA ought to become His Majesty's 16th realm.

It would just about make up for losing Barbados.