In message , John
writes

Just to refer to this simple example, at least I can now understand the
situation where my wife's (non railcard) single Zone 1 journey after
9.30 and another after 16.00 always seem to have been charged more than
the 2x £1.60 I believed was correct.

As Paul has said, £1.60 each way is correct for Zone 1, whatever the
time of day. Is it possible that she is changing from NR to LU outside
of Zone 1 (e.g. at Stratford instead of Liverpool Street), without
realising that this is costing more?
--
Paul Terry