As the proclamation "long live the king" rang out in Westminster Abbey, it was a very different atmosphere in Trafalgar Square -- hundreds of protesters booed loudly and chanted "not my king."
The protesters have been there since the morning and were mixed among royals fans. Yellow banners reading "Abolish the Monarchy" waved in the air, dueling with the Union Jack flags held by people celebrating the coronation.
It's rare to see an anti-royal demonstration in the United Kingdom. The number of people who gathered in support of the crown far outnumbered those who were protesting. However, the issues that motivate the protesters, such as the monarchy being out of date and linked to colonialism, are ones that present serious challenges that Charles will immediately face in trying to keep the crown relevant.
Among those challenges that will emerge immediately are countries in the British Commonwealth that are seeking to remove Charles as head of state. Jamaica has signaled its plans to do so soon and there are questions whether Australia could follow in the coming years.
-ABC News' Patrick Reevell