Here is a photo of a similar circular dish (rather than plate) with the Henry Greener 1st lion trademark (generally reckoned to be found on pieces between 1875 and 1885) PLUS a lozenge mark for 8 June 1878 – Parcel 11.
The lozenge is normally associated with Henry Greener’s RD 322393 of that date, but RD 322393 is actually for a completely different pattern than Roy’s plate. The lozenge is, in fact, one of those curious ‘abberant’ Henry Greener lozenges where it appears on unrelated designs either by design or accident, possibly where a marked plunger from one design is used in a completely different (though similarly sized and shaped) mould.
Here are also photos of other pieces (creamer and celery in clear glass and a jug or pitcher in deep cobalt blue glass) all with the same ‘fans and fan roundels’ decorative pattern as Paul's plate, and all marked with the Henry Greener 1st lion trademark but without registry date lozenges.
It would seem, therefore, that the ‘fans and fan roundels’ design is an unregistered Henry Greener pattern dating from between 1875 and 1885.