Why do these 'well to do' characters all have inbred sounding names?
An interesting facet to this story about Ms Jordan Barber, is that she took on a double-barrelled name on marriage to a young army officer, now 2ic of a very well-known Scottish battalion. She was able to hide this extra income - it seems even from her husband - by alluding to a small estate and family money Conflated with a posh accent, a signet ring and her kids at St Cakes' Prep School, no one seemed to question this apparent display of old money, for a mid-ranked civil servant, earning about the same as a Flt Lt. There will be fellow PPruners who know this insufferable woman from Main Building, and more recently, the wives' circuit at Shrivenham (they left last summer).
I suspect that the CPS selected the corruption in public office charges rather than ones from the OSA to avoid the public interest 'defence'.
The other point, about OSA, is that it is universal in its application. No one needs to sign it for it to apply, exactly the same as for other legislation.