Four Juniors And A German (part three)

PLAYED much too passively in round three of the 69th Hampstead U2200 on Saturday 'evening' (the round began at 5.30pm).

Black to make his 39th move in Aditya Verma (2071/195) - Spanton (1906/171), but you will not be able to guess what I came up with

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39...Kf8??
Well, that is the move I executed on the board. It is illegal, of course, so under the latest Fide rules my opponent was given an extra two minutes on his clock - not that he needed it.
I cannot recall doing anything similar before, at least not when, as here, I had plenty of time on my clock. I guess it shows I was tireder than I realised.
A second illegal move would have cost me the game, but that was an academic consideration as White's position is already winning.
After …
39...Kg8?
… the only possibility under the touch-move rule, the game continued:
40.Ke2 Rd5
If 40...Rc1, White plays 41.Na5 with the unanswerable threat of Rd4.
41.Nf4 Kf7 42.Ke1
But not 42.Nxd5?? cxd5 as 43.Rd4? fails to 43...Bb5 (White would, however, have drawing chances with 43.Re3).
42...Be7 43.Nxd5 cxd5 44.Rd4 (1-0, 52 moves)