Lockdown Garden Birding

Nuthatches have bred in woodland close to my house for many years and they often visit our feeders, but they have never attempted to breed in the garden before.  Our garden is a good size but not huge and the nest box is only 2-3 metres from a footpath and road that run alongside our house.  The birds don't appear to be disturbed by our presence in the garden (and we have been gardening quite a bit during the Coronavirus lockdown).

It was interesting to see Blue Tits entering the nest box from time to time when the Nuthatches are presumably well out of the way.  These have been seen removing nesting material!

I purchased the nest box many years ago (probably 20+) and it is rarely used.  It is made of concrete so the Nuthatches should be safe inside.

Nuthatch bringing nesting material.  This appears to be a Beech leaf.

I noticed that the birds always entered the box via the centre hole

However they always leave by the left hole! 
They often peered out of the right hole but never entered or left by it.

A short video of the Nuthatches during nest building.