Congratulations from me as well. What an achievement! Like many on here, I've never really known any other monarch - I was only 2 when our Queen came to the throne - and it would seem so very strange to have Prince Charles, or even Prince William, as our King. Even stranger to hear the word 'King' in our national anthem!
She still has a long way to go, though, to become the longest reigning monarch of all time. That crown is still held by Sobhuza II, King of Swaziland from 1899 to 1982, a total of 82 years, 254 days. Our dear Queen would have to live to around 108 to match that record 