I learnt about this knot 16 years ago from a comment on cpbotha's blog :

https://cpbotha.net/2010/04/07/weekly-head-voices-20-a-lamar...

It has changed my life. I was also part of mountain rescue at the time, and nobody in the team knew about it. Now everyone swears by it.

So if you're part of any kind of first responder team - please tell your colleagues about this knot!