zucchini in england Riddles

As I was going o’er London Bridge, I heard something crack. Not a man in all England can mend that! What is it?

I am a word of five letters. Take away my first and I am the name of what adorns the estate of many of the nobility of England. Take away my first and second, and I am the name of a place where all the world was once congregated. Take away my last, and I am the name of a beautiful mineral. Take away my two last, and I am the name of a fashionable place of resort. I am small in stature but capable of doing a great deal of mischief, as I once did in London in the year 1666. What word am I?