Back to the seven letters centred on the central cell, these reflect the author of a relevant paper from the Journal of the British Astronomical Association, 1985, vol 95, part 6 pp 260-261, and of which the setter is surely aware.
Having followed the Magpie E Grade March issue discussion about things not being mentioned in the preamble being fair game, after posting at the weekend I remembered the phrase which describes a little hidden gem buried in a puzzle, program, DVD or whatever as an inside joke to anyone picking it up... which is - of course - an Easter Egg.
So unless it really is an amazing coincidence - and as the setter's around, they may be able to confirm this - there's a lovely, thematic present hiding in plain sight.