Chris, further to your Zoom request today, I can kick off with two covers:
The first, if I have interpreted it correctly, is Passed by Censor Gould type 5C20 (HMS Brilliant) and the thimble datestamp the rare Gould DD22 (2 known), possibly used in Lerwick. It is backstamped Halifax 11 JA 16.

The second, again please correct me if I'm wrong, seems to be an unrecorded censor, similar to Gould 7A 30s Addressed to whisky distillers (I thought the Navy only drank rum!) in Aberdeen where it was backstamped on 8 JU 1917.

Both seem to have London IS recorded labels, presumably applied there.
Regards
Jim

Thanks Jim

Two nice covers,  Once I've progressed the 'Army' side of Registration plan to look at the Naval and interwar period for the RAF.  This entire subject seems underdeveloped and explored.

Chris