An inside picture for a change!
At this point, the bird outside moves a little closer.
"What's going on out there?"
Not a lot! Neither bird is showing any sign of hostility so I think we can be sure that they are a pair.
Suddenly the bird inside the box jumps up to the hole to have a look and this sends the other bird away.
But not for long. Less than a second later it's back again.
It lands on the roof again.
Look at the crest on the top of this bird's head. This looks like a male to me.
We have observed several sequences of mating bluetits and the male always raises his head feathers beforehand. We have never seen a female do this.
The head feathers of the bird outside are still raised.
He is getting closer, but there are still no signs of any hostility between these two.
Now the female has jumped back down from the hole ...
... so the male moves closer ...
... and a bit closer.
What's happening here then?
Finally, the male goes onto the hole.
"What's it like in there then?"
"It's a funny design!"
The female flies back onto the hole ...
... the male departs ...
... and so does the female.