Thank you for showing this design, Chris. I don't have any photos of it.
It is shown on page 56 of Sowerby pattern book XI (1885) as Sowerby pattern C. 1804 (or possibly G.1804, it's a little difficult to make out which) in a section titled 'cut & engraved sugars and creams'. The illustration also indicates that it from a registered design.
There is a variant of the shape and pattern shown alongside - I | 1804 - described as 'cut' stars. This variant is not, however, shown as from a registered design.
As Paul says, Thompson describes the design as for 'pattern and shape', so perhaps I | 1804 has the shape but not the pattern from the design representation.
I would appreciate it Paul if could indeed acquire the requisite design details for R 10966 from Kew during some future visit (plus, if possible, RD 10967 for comparison and completeness).
The patterns in this section all have a pattern number for a particular basic shape which is prefixed by a capital letter indicating the style of cut or engraved decoration, e.g.
A.1695 cut & obscured; E. 1695 cut; H. 1695 cut & obscured (but with a different design than A. 1695); I | 1695 cut and obscured (with yet another different design)
I | 1805 cut hollows; A. 1805 engraved; B. 1808 engraved (but with a different design to A. 1805); D. 1805 engraved (with yet another design)
I've checked through my reference photos and there seems to be a dearth of examples of these Sowerby cut and engraved sugars and creams, though I can find no particular reason why they should be uncommon.
Just for reference, though, here is a photo of a very plain shape of pedestal bowl (presumably a sugar) with engraved ferns to the bowl - marked with the the Sowerby peacock head but no RD number - the pattern number for which eludes me at the moment. Also a photo of a can or tankard - pattern 1826 on page 88 of pattern book XI (1885) - from the 1888 Glasgow International exhibition, embellished with engraved ferns.
Fred.