In the latest edition of Daynes book, World War Two Censor Marks, N500, the circular PASSED BY CENSOR / R.V. (usually in red), states, is thought to be the initials of the Rev. R. Venn of HMS Warspite.
The attached large envelope, addressed to Hampstead, London, is carrying this mark, and confirms the identity of this mark, the very tiny signature at top right, is that of Lieut (E) D.N. Callaghan appointed to H.M.S. WARSPITE on 27th April 1939.
Frank Schofield
Very nice find that the small signature at the top right corner led to the identification
Regards
Marc