Sudoku tutorial XY Wing – Basic explanation and real world Hard level solve

I usually solve newspaper sudoku puzzles on YouTube but I also like to play harder puzzles at other times. When I saw this "Doc's Hard Level" last week, I noticed it needed an XY Wing to solve it. I thought this might be a good time to try to give an idea of how to use this technique as it seldom occurs in the newspaper sudoku puzzles. It might not be the best tutorial but I think it gives an idea of what to do. I also made a mistake near the end of the video but I went back a couple of steps to sort it out. I hope it's useful to you.

(Thanks to setter John Musgrave for his excellent sudoku puzzles.)