When does the ending start?

While the start point of openings is pretty straightforward (Move 1!) and the middlegame starts when your memorisation of opening theory runs out, the start point of an ending can be a little trickier. When I was writing chess engines (which evaluate positions differently in the ending), I had an arbitrary rule that the ending started when there was less than a Q+R in material (excluding pawns) for each side. The other possible definitions include "when pawn promotion becomes a goal" or "when the king can move about without the risk of getting checkmated".
It is the last definition that I use most often when coaching. Of course it does depend upon on recognising all the threats in the position, and there are plenty of endings that have ended in checkmate.
A kind of counter-example (in a different sense) turned up from last nights first round of the London Chess Classic (the reason why this post is late btw). The Grischuk - Nakamura game started off with a Berlin Defence to the Ruy Lopez (which is an opening known for a quick transition to an ending). On move 18 Grischuk decided that the king could be used as a fighting piece and moved it up the board. This was a brave decision as there were still plenty of pieces on the board (2R+3 minors each), and it was no surprise that found itself surrounded 10 moves later. However Grischuk had just enough the avoid getting mated and in the end Nakamrua had a repetition but no more.


Grischuk,Alexander - Nakamura,Hikaru [C67]
London Chess Classic Olympia, London (1.5), 04.12.2015

1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. O-O Nxe4 5. d4 Nd6 6. Bxc6 dxc6 7. dxe5 Nf5 8. Qxd8+ Kxd8 9. h3 Ke8 10. Nc3 Be6 11. g4 Ne7 12. Nd4 Bd7 13. Kh2 c5 14. Ndb5 Kd8 15. Be3 a6 16. Na3 b6 17. Ne4 h5 18. Kg3 hxg4 19. hxg4 Bc6 20. Ng5 Ke8 21. f4 f5 22. Rad1 g6 23. Ne6 fxg4 24. Nxc7+ Kf7 25. e6+ Kg8 26. Kxg4 Ra7 27. Rd7 Nf5 28. Bf2 Nh6+ 29. Kg3 Nf5+ 30. Kg4 Be7 31. Rfd1 Nh6+ 32. Kg3 Nf5+ 33. Kg4 Nh6+ 34. Kg3 Rh7 35. Nc4 Nf5+ 36. Kg4 Nh6+ 37. Kg3 Nf5+ 38. Kg4 Nh6+ 1/2-1/2