With motorcades, pomp and pageantry, and uniformed marines festooned in gold and shiny buttons and bayonets, the purpose of America's presidential inauguration is simple: it is pure political theatre.

And while businessman-turned-president Donald Trump may still be finding his size 12 feet in the political arena, he took to the stage today a man in the space he finds most comfortable, playing the star of the show.

In terms of staging, you could not have set the scene more perfectly: the weather in Washington DC was damp and grey, and in California and New York, the two states arguably watching proceedings with the greatest measure of shock, it was appropriately pouring with rain.

Much like it was for many of the 44 men who came before him, Trump's swearing in as the 45th president of the United States came with its ritualistic touches: golden eagle-topped staves and a hand laid gently, and meaningfully, on the Bible.