While the fight is starting inside the box, the third bluetit is clearly taking a close interest. Whether this bird is the partner of the newcomer who first came to the box, or the incumbent who rushed in more recently, is not clear.
Whoever's partner she is, she's clearly very interested in the outcome!
At this point, I thought that one of the bluetits was giving up and was on his way out.
So did the bluetit outside as she started back in surprise.
Perhaps it was the sight of his partner that did the trick. Whatever it was, he decided to continue the fight after all.
The bird outside has perched out of the way. I suppose she doesn't want to get in the way of an escaping bird!
There're still at it ...
... and again a couple of seconds later.
Is this the end?
Surely it must be over now?
But no - at the very last minute, the bluetit that was about to depart changed his mind and went back to continue the fight.
The fight continued!
The two birds appear to be locked into the "deadly embrace" position. Having now seen quite a few fights, I can recognise the position in which each bird has hold of its opponents claws as leading to a stalemate.
At this point they have been at it for about 1½ minutes. They stay in this position for the next 20 minutes!