I have one of the relatively modern electricity meters with a digital
display and when I went to read it today to send in the reading, the
display was reading alternately the power consumed and "rEd".
Additionally a red led is permanently on.

The make of the meter is 'Ampy' - Black and about 100 x 150 x 40mm

Can anyone confirm what this means please?

I have recently had a solar PV system fitted which can feed power back
into the grid. The meter was not changed to accommodate this (instead I
have my own generation meter) so I wonder if it is just an indcation
that the meter has tried to run backwards which would normally happen if
someone was trying to fiddle the meter reading but in my case just shows
the Solar PV has been generating more power than I have been consuming.

TIA

Bob