This
is the second time today we have seen a great tit around Box1.
He
jumps down from the roof onto the entrance hole.
He
appears to be uncertain as to whether he can get inside the box - or perhaps
whether he could get out again if he did go through it! He keeps
trying it for size but never makes a really determined effort to go in.
Shortly
after he flies off again.
Ten
seconds later he is back for another look.
But
again he gives up without appearing to try very hard.
Half
a minute later he is back again! Is that the third or fourth time?
There
he is back on the entrance hole.
But
no - the hole doesn't get any bigger between his visits!
This
time he must have gone right away because immediately the great tit leaves,
the bluetit dashes into the nest box ... 
... and immediately takes up a defensive posture. This is a bit like
shutting the stable door after the horse has bolted as there is no sign of
any great tit outside, but you can understand a bluetit's reluctance to
tangle with a great tit.
Slowly
he calms down.
After
a while, he jumps up to look outside. Presumably he is trying to see
whether the danger is now over.
Clearly,
he could see no sign of the great tit and so felt free to leave the nest box
again.The nest box hole is 28mm and this episode reinforces yet again that the RSPB's recommendation of a 25mm hole for a bluetit and a 28mm hole for a great tit is too small for the tits in Mayford! We have only once seen a great tit manage to go through a 28mm hole and that was much too tight for comfort.