Definitely gazetted Admin & Special Duties Branch, but honour not RAF service related, PN:
"SUPPLEMENT to The London Gazette 9 June 1955 3269
...
To be Ordinary Officers of the Civil Division of the said Most Excellent Order:
...
Ronald Dallas BRETT, Esq., Principal, Ministry of Housing and Local Government."
Postscript
WW I: 1918 LG online search on Ronald Dallas Brett or RD Brett in any order draws no result. Query: WW I airman?
No further information or resource good luck with searching farewell