And what would happen if I touched in at Brockley, then did nothing
else before touching out at Brockley an hour later?

My understanding of how that situation works with same station entry and
exit may be completely wrong or out of date. I thought that if you touch in
and back out very quickly at the same station - something like up to two
minutes - you'll be charged the maximum cash fare (or whatever the correct
term is) but if you then made another entry at the same or another station
within a certain period of time another maximum fare would not be deducted.
So basically it would be assumed you had a genuine reason for coming back
through the gateline quickly (forgotten or dropped something, come in wrong
entrance or something) and were still going to make a journey.

I then thought that if there was a longer period between entry and exit
you'd be charged a single zone fare from that station. Not sure of the
period, something like up to half an hour. I'm not really sure what the
reasoning behind that one is.

Then I thought for even longer periods, which I would have thought would
include your hour long journey, you'd be considered to have make one journey
without an exit, and then another one without an entry and so be debited
another maximum fare in addition to the one on entry. Or if your station
has entry/exit validators instead of a gateline you would be considered to
have made one journey without an exit and were now starting another one.