Bosuns chair: at 21 meters height in the mast

What do you do when you arrive in the harbor and you like to lower your rolled code-0 sail and it won't come down? There is a twist in the line of your sail. At the top of the mast of 21 meters high. The twist is so strong, that trying to turn the sail the opposite site won't help. Only one solution: put on the bosun's chair and hoist to the top of the mast to untwist the line. That's what I did to make the twist go away, so we could lower our sail successfully.