I'm a minor traveling alone internationally...?

What will I need to get through customs/immigration? I'm going to England and I heard you need a note from your parents? What does this note have to say? Where can I get information on this?

Yikes! A note? I went to London a lot when I was younger on my own and I didn't need a note. Just a passport!

I'm from the UK and I can tell you all you need is your passport.

You need your passport and boading pass obviously and the note needs to be official and signed saying that you can fly abroad alone, the destination, why your going there and who will pick you up at the other side