Viewer-requested Extreme Killer Sudoku - Not For The Faint-Hearted 

And you thought a 30 minute puzzle was long! I enjoyed this throwback. Your production value has greatly increased over the years.

that move at 21:00 is insanely smart

Intriguing. Too advanced for me, but I think I can identify all the cages in box 9 after the initial 2. By the 'secret', there are 2 cells that add to 9, and could be 3 + 6 or 4 + 5. That means the 11 cage cannot be 5 + 6, so is therefore 4 + 7. The odd cells in R7 adding to 9 are reduced to 3 + 6. The 3 in box 9 can now only go in the 9 cage with a 6. The 1 goes in the 10 cage with 9, and the 13 cage is 5 & 8. (I hope I didn't figure that wrong!)

Regarding the uniqueness: Ive come across daily killer sudokus that had more than one solution.

As enjoyable to watch as it was for you to solve. Some cracking scenario - exploring as always.

My faint heart becomes a little more stalwart when it's possible to relax and enjoy your excellent work in getting the solution.

Simon may not like to bifuricate but he sure is good at it!

The secret sounded a lot different 4 years ago.

This was pretty rough, just in terms of finding the right questions to ask. That 14 cage had so much power over the back half of the solve, in my case combined with the 11 cage in box 1.

Simon bifurcating and using uniqueness!

I actually found this to be a relatively easy 10 difficulty puzzle.