I had played well to reach this position and the next move seems obvious.
The simple 25…Qg4+ 26.Kh1 Qh6 wins easily with the twin threats of mate on h7 and mate on f8. However I actually played 26…Nh4 which allowed White an opportunity to escape which he duly did.
I have been trying to fathom how I could miss such a simple move. I moved too quickly and I played down a line which I had looked at a few moves ago without checking.
Let’s hope this is a lesson learnt.